EP4397673A1 - Compound and labeled biomaterial using same - Google Patents

Abstract

There are provided a compound having at least two phosphor moieties and a structure represented by General Formula (I), and a labeled biological substance.

In the formula, X¹ to X³ represent -O-, -S-, >NR¹, or >CR²R³. R¹ to R³ represent a hydrogen atom or a substituent. L^a and L^b represents a single bond or a divalent linking group. n is an integer of 2 or more.

However, at least one among R¹ to R³, which are contained in a structure parenthesized in ( )_n, L^a, and L^b includes -(L-O)_gR^E, where -(L-O)_gR^E in each of these groups is not bonded to at least any one of a phosphor or a biological substance.

L represents an alkylene group, R^E represents a hydrogen atom or an alkyl group, and g is 1 to 24.

* represents a bonding site.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention
• The present invention relates to a compound and a labeled biological substance using the compound.
2. Description of the Related Art
• In order to observe in vivo changes in response to various stimuli (diseases, environmental changes, and the like), fluorescently labeled biological substances obtained by labeling a biological molecule (an antibody or the like) having a binding property to a target substance to be detected, with a fluorescent compound (a fluorescent dye), are often used.
• For example, also in Western blotting (hereinafter, also abbreviated as WB) that detects a specific protein from a protein mixture, a fluorescence method in which the presence or absence or the abundance of the specific protein is detected using a fluorescently labeled antibody having a binding property to this protein is used.
• In addition, in bioimaging technology for analyzing the dynamics and functions of biological molecules, cells, tissues, and the like in a living body, in vivo fluorescence imaging in which a specific portion of a living body visualized by fluorescence labeling is observed is used as one of the techniques for the living body observation.
• In the fluorescence labeling, an organic fluorescent dye molecule is generally used, and the brightness (fluorescence intensity) is increased generally by using a fluorescently labeled biological substance to which a plurality of fluorescent dye molecules are bonded. However, since most of the organic dyes exhibiting fluorescence, such as a cyanine dye and a rhodamine dye, have an aromatic chromophore having high planarity, an interaction between the dyes easily occurs, and as a result, a decrease in the fluorescence intensity after labeling due to an interaction such as self-association between the dyes easily occurs. In addition, as the number of molecules (degree of fluorescence labeling: DOL) of the fluorescent dye per one molecule of the biological molecule increases, the fluorescence intensity due to self-association or the like tends to further decrease.
• On the other hand, in a field different from the fluorescence labeling, a dye compound that utilizes a fluorescence resonance energy transfer (FRET) phenomenon is known. As a dye compound that utilizes such a FRET phenomenon, for example, a compound in which a phosphor moiety I (an energy donor) that is excited with excitation light is linked, by a peptide chain of amino acids including proline, to another phosphor moiety II (an energy acceptor) that receives energy from the phosphor moiety I and emits light or is quenched is described as described in "Synthesis of Polyproline Spacers between NIR Dye Pairs for FRET to Enhance Photoacoustic Imaging".
• In addition, JP2018-521308A describes a method for subjecting a molecule to sequence determination based on luminescence life and/or luminescence intensity and describes a compound in which a dye and a nucleotide are bonded by a linker moiety including a polyethylene glycol structure, as a luminescent labeled nucleotide that is used in a sequence determination method for a nucleic acid.
SUMMARY OF THE INVENTION
• A dye that is used for fluorescence labeling is required to exhibit an excellent fluorescence intensity in various states of being in a solution, a membrane, and the like. However, in such dye compounds described above, which utilize the FRET phenomenon, as described in "Synthesis of Polyproline Spacers between NIR Dye Pairs for FRET to Enhance Photoacoustic Imaging", the energy is transferred to the phosphor moiety II instead of emitting fluorescence from the phosphor moiety I, and thus the fluorescence intensity of the compound is decreased. In addition, as described in JP2018-521308A , in a case where a polyethylene glycol structure is provided in the main chain structure of the linker moiety that connects a dye to a nucleotide, a sufficient excluded volume effect cannot be obtained as compared with a case where the polyethylene glycol structure is provided as a substituent, and the dyes are associated, whereby the fluorescence intensity is decreased.
• An object of the present invention is to provide a compound that makes it possible to obtain a labeled biological substance exhibiting an excellent fluorescence intensity even in any state of being in a solution or a membrane. In addition, another object of the present invention is to provide a labeled biological substance obtained by bonding the compound to a biological substance.
• That is, the above objects of the present invention have been achieved by the following means.
1. [1] A compound comprising:
   • at least two phosphor moieties; and
   • a structure represented by General Formula (I),
     
   • in the formula, X¹ to X³ represent -O-, -S-, >NR¹, or >CR²R³,
   • R¹ to R³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, -(L-O)_gR^E, an acyl group, -NR⁸R⁹, or -OR¹⁰,
   • R⁸ to R¹⁰ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an aryl group, a heteroaryl group, or -(L-O)_gR^E, where L represents an alkylene group, R^E represents a hydrogen atom or an alkyl group, and g is 1 to 24,
   • L^a and L^b represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, where
   • R^A and R^B represent a hydrogen atom or a substituent,
   • n is an integer of 2 or more,
   • provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and/or at least one of L^a or L^b is a group having, as a substituent, a group including -(L-O)_gR^E,
   • the -(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance, and
   • * represents a bonding site.
2. [2] The compound according to [1], in which the compound is represented by General Formula (II),
   
   • in the formula, R⁴ and R⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group,
   • R⁶ and R⁷ represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, an amino group, an acyl group, a heteroaryl group, an anionic group, a cationic group, or Q, where Q represents a carboxy group, a substituent capable of being bonded to a biological substance, or a substituent capable of being bonded to a solid support,
   • L¹ and L⁶ represent an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, or >P(=O)OR^B,
   • L² and L⁵ represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B,
   • M represents the phosphor moiety, a physiologically active substance moiety, a prodrug moiety, or a radioactive isotope-containing moiety,
   • provided that at least two of M's represent the phosphor moiety,
   • m is an integer of 1 or more,
   • X¹ to X³, R¹ to R³, L^a, L, R^A, R^B, R^E, g, and n respectively have the same meanings as X¹ to X³, R¹ to R³, L^a, L, R^A, R^B, R^E, g, and n described above,
   • provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and/or at least one of L^a, L³, or, L⁴ is a group having, as a substituent, a group including -(L-O)_gR^E, and
   • the -(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
3. [3] The compound according to [2], in which the compound is represented by General Formula (III),
   
   • in the formula, Y¹ to Y³, Z¹ to Z³, and W¹ to W³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group,
   • LL¹ and LL² represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B,
   • s, t, and u are an integer of 0 or more,
   • R¹ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, L, R^A, R^B, R^E, g, n, and m respectively have the same meanings as R¹ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, L, R^A, R^B, R^E, g, n, and m described above,
   • provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and/or at least one of Y¹, Y², Y³, Z¹, Z², Z³, W¹, W², or W³ is a group including -(L-O)_gR^E, and
   • the -(L-O)_gR^E in R¹ to R³, Y¹ to Y³, Z¹ to Z³, and W¹ to W³, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
4. [4] The compound according to [3], in which the compound is represented by General Formula (IV),
   
   • in the formula, R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q,
   • provided that at least one of R^6A or R^7A represents Q,
   • L⁷ and L⁸ represent a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B,
   • Y⁴ and Y⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group, and
   • R⁴, R⁵, L², L⁵, X¹ to X³, Y¹ to Y³, Z¹ to Z³, W¹ to W³, M, Q, R^A, R^B, n, m, s, t, and u respectively have the same meanings as R⁴, R⁵, L², L⁵, X¹ to X³, Y¹ to Y³, Z¹ to Z³, W¹ to W³, M, Q, R^A, R^B, n, m, s, t, and u described above.
5. [5] The compound according to [3] or [4], in which at least one of the following condition (Z1), (Z2), or (Z3) is satisfied,
   • the condition (Z1): the s is an integer of 1 or more, and at least one of the Y¹, the Z¹, or the W¹ is a group including -(L-O)_gR^E,
   • the condition (Z2): the t is an integer of 1 or more, and at least one of the Y², the Z², or the W² is a group including -(L-O)_gR^E,
   • the condition (Z3): the u is an integer of 1 or more, and at least one of the Y³, the Z³, or the W³ is a group including -(L-O)_gR^E.
6. [6] The compound according to any one of [1] to [5], in which the structure represented by General Formula (I) includes a structure in which X¹ to X³ are >CR²R³.
7. [7] The compound according to [6], in which in the structure in which X¹ to X³ are >CR²R³, where the structure is included in the structure represented by General Formula (I), at least one R² is -NR⁸R⁹ or -OR¹⁰.
8. [8] The compound according to [7], in which in a structure in which X¹ to X³ are >CR²R³ and at least one R² is -NR⁸R⁹, or -OR¹⁰, where the structure is included in the structure represented by General Formula (I), at least one of R⁸, R⁹, or R¹⁰ is a group including -(L-O)_gR^E
9. [9] The compound according to [2], in which the compound is represented by General Formula (V),
   
   • in the formula, X⁴ to X⁹ represent -O-, -S-, >NR¹⁰¹, or >CR¹⁰²R¹⁰³,
   • provided that one of X⁴, X⁵, or X⁶ is a carbon atom or a nitrogen atom, which has -L¹⁰-M as any one of R¹⁰¹, R¹⁰², or R¹⁰³, and one of X⁷, X⁸, or X⁹ is a carbon atom or a nitrogen atom, which has -L¹¹-M as any one of R¹⁰¹, R¹⁰², or R¹⁰³,
   • R¹⁰¹ to R¹⁰³, which are neither -L¹⁰-M nor -L¹¹-M, represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an acyl group, -NR⁸R⁹, -OR¹⁰, or an anionic group,
   • L¹⁰ and L¹¹ represent a single bond or a divalent linking group,
   • R¹ to R³, R⁶ to R¹⁰, X¹ to X³, M, n, and m respectively have the same meanings as R¹ to R³, R⁶ to R¹⁰, X¹ to X³, M, n, and m described above,
   • provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and
   • R¹ to R³ which include the -(L-O)_gR^E are not bonded to at least any one of a phosphor or a biological substance.
10. [10] The compound according to [9], in which the compound is represented by General Formula (VI),
    
    • in the formula, R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q,
    • provided that at least one of R^6A or R^7A represents Q,
    • L¹² and L¹³ represent a linking group,
    • na and nb are integers of 0 or more, and
    • L¹⁰, L¹¹, X¹ to X⁹, M, Q, n, and m respectively have the same meanings as L¹⁰, L¹¹, X¹ to X⁹, M, Q, n, and m described above,
    • provided that any structure parenthesized in ( )_n, ( )_na, or ( )_nb has at least any one of >NR¹ or >CR²R³, and each of the structures parenthesized in ( )_n, ( )_na, and ( )_nb has a group including -(L-O)_gR^E, as at least one of R¹, R², or R³, and
    • R¹ to R³ which include the -(L-O)_gR^E are not bonded to at least any one of a phosphor or a biological substance.
11. [11] The compound according to [10], in which (A) the na is an integer of 1 or more, and the R^6A is the Q, and/or (B) the nb is an integer of 1 or more, and the R^7A is the Q, provided that the number of shortest linking atoms of the L¹³ is 7 or less in a case of the (A), and the number of shortest linking atoms of the L¹² is 7 or less in a case of the (B).
12. [12] The compound according to any one of [9] to [11], in which the structure represented by General Formula (I) includes a structure in which X¹ to X³ are >CR²R³.
13. [13] The compound according to [12], in which in the structure in which X¹ to X³ are >CR²R³, where the structure is included in the structure represented by General Formula (I), at least one R² is -NR⁸R⁹ or -OR¹⁰.
14. [14] A labeled biological substance that is obtained by bonding the compound according to any one of [1] to [13] to a biological substance.
15. [15] The labeled biological substance according to [14], in which the biological substance is any one of a protein, an amino acid, a nucleic acid, a nucleotide, a sugar chain, or a phospholipid.
• The compound according to the aspect of the present invention makes it possible to obtain a labeled biological substance exhibiting an excellent fluorescence intensity in any state of a solution, a membrane, or a dot blot. In addition, the labeled biological substance according to the aspect of the present invention exhibits an excellent fluorescence intensity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
• In the present invention, in a case where there is a plurality of substituents, linking groups, structural units, or the like (hereinafter, referred to as substituents or the like), which are represented by a specific symbol or Formula, or in a case where a plurality of substituents or the like are regulated at the same time, the substituents or the like may be the same or different from each other, unless otherwise specified. The same applies to the regulation of the number of substituents or the like. In addition, in a case where a plurality of substituents or the like come close to each other (particularly in a case where they are adjacent to each other), they may be linked to each other to form a ring, unless otherwise specified. In addition, unless otherwise specified, rings such as an alicyclic ring, an aromatic ring, and a heterocyclic ring may be fused to form a fused ring.
• For example, in the present invention, a structure excluding L^a and L^b in the structure represented by General Formula (I) described below means that n (n is an integer of 2 or more) pieces of structures represented by General Formula (i) are connected. In this case, the n pieces of structures represented by General Formulae (i) may be the same or different from each other. It is noted that X¹ to X³ in General Formula (i) respectively have the same meanings as X¹ to X³ in General Formula (I) described later. The same applies to a structure parenthesized in ( )_s, a structure parenthesized in ( )_t, a structure parenthesized in ( )_u, a structure parenthesized in ( )_m, a structure parenthesized in ( )_na, and a structure parenthesized in ( )_nb, where s pieces of structures may be the same or different from each other, t pieces of structures may be the same or different from each other, u pieces of structures may be the same or different from each other, m pieces of structures may be the same or different from each other, na pieces of structures may be the same or different from each other, and nb pieces of structures may be the same or different from each other.

  
• In the present invention, in a case where an E type and a Z type of a double bond are present in a molecule, any one of the E type or the Z type, or a mixture thereof may be used unless otherwise specified. In addition, unless otherwise specified, in a case where a chiral carbon atom or a chiral center is present in a compound, the steric conformation may be any of R or S in the R-S notation, and a mixture thereof may be may be allowed.
• In the present invention, the denotation of a compound or substituent is meant to include not only the compound itself but also a salt thereof, and an ion thereof. For example, the dissociable anionic group such as the carboxy group, the sulfo group, and the phosphono group (-P(=O)(OH)₂) may have an ionic structure by a hydrogen ion being dissociated therefrom, or they may have a salt structure. That is, in the present invention, the "carboxy group" is meant to include a group of an ion or salt of a carboxylic acid, the "sulfo group" is meant to include a group of an ion or salt of a sulfonic acid, and the "phosphono group" is meant to include a group of an ion or salt of a phosphonic acid. The monovalent or polyvalent cation in forming the salt structure is not particularly limited. Examples thereof include an inorganic cation and an organic cation, and specific examples thereof include alkali metal cations such as Na⁺, Li⁺, and K⁺, alkaline earth metal cations such as Mg²⁺, Ca²⁺, and Ba²⁺, and organic ammonium cations such as a trialkylammonium cation and a tetraalkylammonium cation.
• In a case of a salt structure, the kind of the salt may be one kind, two or more kinds thereof may be mixed, a salt-type group and a group having a free acid structure may be mixed in a compound, and a compound having a salt structure and a compound having a free acid structure compound may be mixed.
• Any compound according to the embodiment of the present invention is a neutral compound. In the present invention, the fact that the compound is neutral means that the compound is electrically neutral. Specifically, the charge of the compound as a whole is adjusted to be 0 by a group having a charge or by a counterion in the compound. For example, in the cyanine dye represented by General Formula (α), which is exemplified as an example of the dye that constitutes the phosphor moiety, the formal charge of the nitrogen atom to which R⁴² is bonded is +1, and the dissociable group such as a sulfo group in another structure of the cyanine dye or the compound according to the embodiment of the present invention has an ionic structure such as a sulfonate ion to be paired with this formal charge, whereby the compound according to the embodiment of the present invention is to be a compound having a charge of 0 as a whole.
• In each general formula pertaining to the cyanine dye, which is defined in the present invention, the positive charge possessed by the compound is specified and indicated, for convenience, as a structure of a specific nitrogen atom. However, since the cyanine dye defined in the present invention has a conjugated system, another atom other than the nitrogen atom actually may be capable of being positively charged, and thus any cyanine dye capable of adopting a structure represented by each general formula as one of the chemical structures is included in the cyanine dye represented by each general formula. This also applies to the negative charge.
• In addition, it is meant to include those in which a part of the structure is changed within the scope that does not impair the effect of the present invention. Further, it is meant that a compound, which is not specified to be substituted or unsubstituted, may have any substituent within the scope that does not impair the effect of the present invention. The same applies to a substituent (for example, a group represented by "alkyl group", "methyl group", "methyl") and a linking group (for example, a group represented by "alkylene group", "methylene group", "methylene"). Among such substituents, a preferred substituent in the present invention is a substituent selected from a substituent group T described later.
• In the present invention, in a case where the number of carbon atoms of a certain group is specified, this number of carbon atoms means the number of carbon atoms of the entire group thereof unless otherwise specified in the present invention or the present specification. That is, in a case where this group has a form that further has a substituent, it means the total number of carbon atoms, to which the number of carbon atoms of this substituent is included.
• In addition, in the present invention, the numerical range represented by using "to" means a range including the numerical values before and after "to" as the lower limit value and the upper limit value, respectively.
• The compound according to the embodiment of the present invention is a compound having at least two phosphor moieties and a structure represented by General Formula (I) described later. Although the details of the reason why the compound according to the embodiment of the present invention makes it possible to obtain a labeled biological substance exhibiting an excellent fluorescence intensity in both states of being in a solution and a membrane are not clear, they can be conceived as follows.
• It is known that, in general, in a compound having at least two phosphor moieties in the molecule, the quenching due to the intramolecular or intermolecular association of the phosphor moieties, that is, the decrease in the fluorescence intensity easily occurs as compared with a compound having one phosphor moiety in the molecule. On the other hand, the compound according to the embodiment of the present invention is a compound having at least two phosphor moieties, where it includes a relatively rigid structure consisting of a repeating unit (the repetition number n is an integer of 2 or more) containing a nitrogen-containing saturated 5-membered ring such as a ring structure derived from proline, as represented by General Formula (I) described below, and thus the quenching due to the association of the phosphor moieties can be suppressed. Further, the structure represented by General Formula (I) described later has a polyalkyleneoxy group represented by -(L-O)_gR^E in addition to the repeating unit containing the nitrogen-containing saturated 5-membered ring, and thus the polyalkyleneoxy group present in the vicinity of the above-described relatively rigid structure can effectively exhibit the excluded volume effect. As a result, it is conceived that a labeled biological substance obtained by using the compound according to the embodiment of the present invention can exhibit an excellent fluorescence intensity.
• Hereinafter, the compound according to the embodiment of the present invention will be described in detail.
<Compound according to embodiment of present invention>
• The compound according to the embodiment of the present invention is a compound having at least two phosphor moieties and a structure represented by General Formula (I) described later.
• The compound according to the embodiment of the present invention may be a compound classified into a polymer or an oligomer.
• It is sufficient that the phosphor moiety is contained in the compound according to the embodiment of the present invention in a state of being bonded, directly or through a linking group, to the bonding site * in General Formula (I), as a structure different from the structure represented by General Formula (I). Examples of the form in which the phosphor moiety is bonded to the bonding site * in General Formula (I) directly or through a linking group include a compound represented by General Formula (II) described later.
• It is preferable that in the compound according to the embodiment of the present invention, the phosphor moieties adjacent to each other are linked through a structure represented by General Formula (I), that is, it is preferable that the compound according to the embodiment of the present invention is a compound in which two structures having a phosphor moiety as a substituent are linked through a group including a structure represented by General Formula (I).
• It is noted that the structure having, as a substituent, a phosphor moiety that is bonded to the bonding site * in General Formula (I), is not particularly limited. For example, the structure may have in addition to the structure represented in General Formula described later, as a substituent, a group in which a 5-membered ring contains a phosphor moiety, where the 5-membered ring described in the structure represented by General Formula (I) is formed to have a carbon atom, a nitrogen atom, and X¹ to X³ as ring-constituting atoms by a combination of L¹ and L², a combination of L¹ and L^a, a combination of L⁴ and L⁵, or a combination of L⁴ and L⁶, as described in detail in General Formula (II) described later. That is, as long as being bonded to the bonding site * in General Formula (I), the structure having a phosphor moiety as a substituent may be a structure in which the 5-membered ring described in the structure represented by General Formula (I), which has a carbon atom, a nitrogen atom, and X¹ to X³ as ring-constituting atoms, has a group in which a phosphor moiety is contained as a substituent. Examples of such a compound include a compound represented by General Formula (V) or (VI) described later.
• The description, the specific examples, and the like of the phosphor moiety in General Formula (II) described later can be applied to the phosphor moiety contained in the compound according to the embodiment of the present invention.
(Structure represented by General Formula (I))
• 
• In the formula, X¹ to X³ represent -O-, -S-, >NR¹, or >CR²R³.
• R¹ to R³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, -(L-O)_gR^E, an acyl group, -NR⁸R⁹, or -OR¹⁰.
• R⁸ to R¹⁰ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an aryl group, a heteroaryl group, or -(L-O)_gR^E.
• L represents an alkylene group, R^E represents a hydrogen atom or an alkyl group, and g is 1 to 24.
• L^a and L^b represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B. R^A and R^B represent a hydrogen atom or a substituent.
• n is an integer of 2 or more.
• * represents a bonding site.
• However, the structure represented by General Formula (I) satisfies the following definitions (α) and (β).
• Definition (α): The following definition (α1) and/or (α2) is satisfied.
• Definition (α1): A structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E.
• Definition (α2): At least one of L^a or L^b is a group having, as a substituent, a group including -(L-O)_gR^E.
• Definition (β): The -(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
• In the definition (α1), the phrase "at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E" means that the at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is -(L-O)_gR^E, is an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, or an acyl group, which has -(L-O)_gR^E as a substituent, or is a group represented by -NR⁸R⁹ or -OR¹⁰, where at least one of R⁸, R⁹, or R¹⁰ is a group having, as a substituent, a group including -(L-O)_gR^E. It is noted that the description that at least one of R⁸, R⁹, or R¹⁰ is a group having, as a substituent, a group including -(L-O)_gR^E means that at least one of R⁸, R⁹, or R¹⁰ is -(L-O)_gR^E or is an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an aryl group, or a heteroaryl group, which has -(L-O)_gR^E as a substituent.
• The description pertaining to the definition (α1) can be similarly applied to a definition (α2-b) in a compound represented by General Formula (III) which will be described later.
• The definition (α2) means that at least one of L^a or L^b is a divalent group having, directly or through a linking group, a group represented by -(L-O)_gR^E. Specifically, it means that at least one of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, >NR^A, or >P(=O)OR^B, which can constitute L^a or L^b, has, as a substituent, a group including -(L-O)_gR^E.
• In the definition (α2), in a case where L^a has, as a substituent, a group including -(L-O)_gR^E, it is preferable that the atom at the 1st to 12th position has, as a substituent, a group including -(L-O)_gR^E, it is more preferable that the atom at the 1st to 6th position has, as a substituent, a group including -(L-O)_gR^E, and it is still more preferable that the atom at the 1st to 3rd position has, as a substituent, a group including -(L-O)_gR^E, in a case of setting a position of a nitrogen atom having a bonding site in the structure parenthesized in ( )_n, as the 0th position, and carrying out counting from this nitrogen atom. Similarly, also in a case where L^b has, as a substituent, a group including -(L-O)_gR^E, it is preferable that the atom at the 1st to 12th position has, as a substituent, a group including -(L-O)_gR^E, it is more preferable that the atom at the 1st to 6th position has, as a substituent, a group including -(L-O)_gR^E, and it is still more preferable that the atom at the 1st to 3rd position has, as a substituent, a group including -(L-O)_gR^E, in a case of setting a position of a carbon atom of >C=O having a bonding site in the structure parenthesized in ( )_n, as the 0th position, and carrying out counting from this carbon atom. For example, in the compound (1) to be used in Examples described later, L^a has, as a substituent, a group including -(L-O)_gR^E, and the carbon atom at the second position in a case of carrying out counting from the nitrogen atom (at the 0th position) having a bonding site in the structure parenthesized in ( )_n has -C₄H₈NHC(=O)-(C₂H₄O)₄CH₃.
• The description pertaining to the definition (α2) can be similarly applied to a definition (α2-a) in a compound represented by General Formula (III) which will be described later.
• The definition (β) means that L and R^E that constitute the -(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
• It is noted that the phosphor means an organic compound (a fluorescent dye) that exhibits fluorescence, which will be described in the phosphor moiety described later, and the biological substance means a biological substance that is described in the labeled biological substance described later.
• The description pertaining to the definition (β) can be similarly applied to a definition (β-a) in a compound represented by General Formula (II) which will be described later and a definition (β-b) in a compound represented by General Formula (III) which will be described later.
• In a case where the structure represented by General Formula (I) satisfies the definition (α) but does not satisfy the definition (β), an excluded volume effect due to -(L-O)_gR^E cannot be sufficiently obtained as compared with a case where the definition (α) and the definition (β) are satisfied, whereby the dyes are associated, and the fluorescence intensity is inferior.
• In the present invention, the structure parenthesized in ( )_n in the structure represented by General Formula (I) is preferably a structure represented by any one of General Formula (IA) or (IB) in consideration of stereoisomers. It is noted that X¹ to X³ and n in the following general formula respectively have the same meanings as X¹ to X³ and n in General Formula (I).

  
• X¹ to X³ represent -O-, -S-, >NR¹, or >CR²R³, and R¹ to R³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, -(L-O)_gR^E, an acyl group, -NR⁸R⁹, or -OR¹⁰.
• The alkyl group, the alkenyl group, the alkynyl group, the aryl group, the heteroaryl group, the acyl group, and -(L-O)_gR^E, which can be adopted as R¹ to R³, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the aryl group, the heteroaryl group, the acyl group, and -(L-O)_gR^E in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof.
• The alkyl group, the alkenyl group, the alkynyl group, the aryl group, the heteroaryl group, and the acyl group, which can be adopted as R¹ to R³, may be unsubstituted or may have a substituent.
• Examples of the substituent which may be contained in the alkyl group, the alkenyl group, the alkynyl group, the aryl group, the heteroaryl group, and the acyl group, as R¹ to R³, include substituents in the substituent group T which will be described later. For example, a halogen atom or -(L-O)_gR^E is preferable.
• In -NR⁸R⁹ and -OR¹⁰, which can be adopted as R¹ to R³, R⁸ to R¹⁰ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an aryl group, a heteroaryl group, or -(L-O)_gR^E.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the aryl group, the heteroaryl group, and -(L-O)_gR^E, which can be adopted as R⁸ to R¹⁰, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the acyl group, the aryl group, the heteroaryl group, and -(L-O)_gR^E in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the aryl group, the heteroaryl group, which can be adopted as R⁸ to R¹⁰, may be unsubstituted or may have a substituent.
• Examples of the substituent which may be contained in the alkyl group, the alkenyl group, the alkynyl group, the acyl group, the aryl group, the heteroaryl group, as R⁸ to R¹⁰, include substituents in the substituent group T which will be described later. For example, a halogen atom or -(L-O)_gR^E is preferable.
• R¹ is preferably a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E.
• R² and R³ are preferably a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E, where it is more preferable that R² is a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E, and R³ is a hydrogen atom.
• R⁸ to R¹⁰ are preferably a hydrogen atom, an alkyl group, an acyl group, or -(L-O)_gR^E, more preferably a hydrogen atom or -(L-O)_gR^E,), or an acyl group having -(L-O)_gR^E as a substituent, and still more preferably a hydrogen atom, -(L-O)_gR^E, or -C(=O)(L-O)_gR^E.
• Regarding X¹ to X³, it is preferable that at least any one thereof is >CR²R³, and it is more preferable that at least two thereof are >CR²R³ and the remaining one is -O-, -S-, or >CR²R³.
• In the present invention, from the viewpoint of making the structure represented by General Formula (I) a more rigid structure, it is preferable that the structure represented by General Formula (I) includes a structure in which X¹ to X³ are >CR²R³. That is, "the structure represented by General Formula (I) includes a structure in which X¹ to X³ are >CR²R³" means that all of X¹ to X³ are >CR²R³ in at least one structure represented by General Formula (i) among n pieces of the consecutive structures represented by General Formula (i) described above. This means that even in a structure corresponding to the structure represented by General Formula (I) among the structures represented by General Formulas (II) to (VI), all of X¹ to X³ are >CR²R³ in at least one structure represented by General Formula (i) among n pieces of the consecutive structures represented by General Formula (i) described above.
• In the structure represented by General Formula (I), the proportion of the number of the structures in which X¹ to X³ are >CR²R³ among n pieces of the consecutive structures represented by General Formula (i) described above is preferably 30% or more, more preferably 60% or more, and still more preferably 80%. The upper limit of the ratio is not particularly limited and may be 100% or less. It is noted that it is also preferable that in the structure represented by General Formula (I), all of the n pieces of the consecutive structures represented by General Formula (i) described above are structures in which X¹ to X³ described above are >CR²R³.
• From the viewpoint of suppressing the intermolecular interaction and furthermore, the intramolecular interaction between structures represented by General Formula (I) in a case where a plurality of structures are present, at least one R² in the above-described structure in which X¹ to X³ is >CR²R³ is preferably -NR⁸R⁹ or -OR¹⁰, and it is more preferably -NR⁸R⁹ or -OR¹⁰, where at least one of R⁸, ..., or R¹⁰ is a group including -(L-O)_gR^E.
• It is noted that the phrase "at least one R² in structure in which X¹ to X³ are >CR²R³ is -NR⁸R⁹ or -OR¹⁰, where at least one of R⁸, ..., or R¹⁰ is a group including -(L-O)_gR^E" means that, in other words, at least one of R⁸ or R⁹ is a group including -(L-O)_gR^E in a case where R² is -NR⁸R⁹, and R¹⁰ is a group including -(L-O)_gR^E in a case where R² is -OR¹⁰.
• In addition, the description that R¹⁰ is a group including -(L-O)_gR^E means that R¹⁰ is -(L-O)_gR^E or is a group having -(L-O)_gR^E as a substituent. The same applies to a case where at least one of R⁸ or R⁹ is a group including -(L-O)_gR^E.
• L^a and L^b represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B. R^A and R^B represent a hydrogen atom or a substituent.
• The alkylene group that can constitute L^a to L^b has the same meaning as the group in which one hydrogen atom is further removed from the alkyl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The alkenylene group that can constitute L^a or L^b has the same meaning as the group in which one hydrogen atom is further removed from the alkenyl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The alkynylene group that can constitute L^a to L^b has the same meaning as the group in which one hydrogen atom is further removed from the alkynyl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The arylene group that can constitute L^a or L^b has the same meaning as the group in which one hydrogen atom is further removed from the aryl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The heteroarylene group that can constitute L^a or L^b has the same meaning as the group in which one hydrogen atom is further removed from the heteroaryl group selected from the substituent group T which is described later, and the same applies to the preferred one thereof.
• The alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L^a or L^b, may be an unsubstituted group or a group having a substituent.
• The substituent which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L^a or L^b, is not particularly limited, and it is preferably selected from a substituent group T described later. More preferred examples thereof include a halogen atom, an alkyl group, an acylamino group, a carbamoyl group, and -(L-O)_gR^E. In addition, the substituent which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L^a or L^b, may be substituted with a substituent selected from the substituent group T which will be described later, and it is, for example, preferably -(L-O)_gR^E.
• In addition, the number of substituents which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L^a or L^b, is not particularly limited as long as it can be adopted as a structure. The number thereof can be set to at least one or more, the upper limit thereof is not particularly limited, and for example, all hydrogen atoms in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group may be substituted with a substituent.
• The substituent which can be adopted as R^A in >NR^A and as R^B in >P(=O)OR^B, which can constitute L^a or L^b, is not particularly limited, and it is preferably selected from the substituent group T which will be described later. R^A is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, or -(L-O)_gR^E, more preferably a hydrogen atom or an alkyl group, and still more preferably a hydrogen atom. R^B is preferably a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heteroaryl group, more preferably a hydrogen atom or an alkyl group, and still more preferably a hydrogen atom.
• It is noted that all the alkyl group, the alkenyl group, the alkynyl group, the aryl group, and the heteroaryl group, which can be adopted as R^A and R^B, may be an unsubstituted group or a group having a substituent.
• The substituent which may be contained in the alkyl group, the alkenyl group, the alkynyl group, the aryl group, and the heteroaryl group, which can be adopted as R^A and R^B, is not particularly limited, and it is preferably selected from a substituent group T described later. More preferred examples thereof include a halogen atom, an alkyl group, and -(L-O)_gR^E. In addition, the substituent which may be contained in the alkyl group, the alkenyl group, the alkynyl group, the aryl group, and the heteroaryl group, which can constitute L^a or L^b, may be substituted with a substituent selected from the substituent group T which will be described later, and it is, for example, preferably -(L-O)_gR^E.
• In the linking group obtained by combining two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, which can constitute L^a or L^b, the kind of the group to be combined is not particularly limited as long as the group to be combined has a reasonable chemical structure; however, it is preferably 2 to 6 kinds and more preferably 2 to 4 kinds. It is noted that in a case of counting, as one kind, each of the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, the maximum number of kinds is 12.
• It is noted that in the linking group obtained by combining two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, which can constitute L^a or L^b, the number of groups to be combined is not particularly limited; however, examples thereof preferably include 2 to 10 groups, more preferably include 2 to 6 groups, and still more preferably 2 to 4 groups.
• L^a and L^b are preferably a single bond, >C=O, >NR^A, or an alkylene group, or a combination of at least one of an alkylene group or an arylene group and at least one of >C=O or >NR^A, and are more preferably a single bond, >C=O, >NR^A, or a combination of an alkylene group and >C=O or >NR^A.
• n is an integer of 2 or more. The lower limit value of n is preferably an integer of 3 or more, more preferably an integer of 7 or more, still more preferably an integer of 9 or more, and particularly preferably an integer of 12 or more. The upper limit value thereof is not particularly limited and can be set to, for example, an integer of 72 or less, and it is preferably an integer of 36 or less, more preferably an integer of 24 or less, and still more preferably an integer of 18 or less.
<Compound represented by General Formula (II)>
• The compound according to the embodiment of the present invention is preferably represented by General Formula (II).

  
• In the formula, R⁴ and R⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group.
• R⁶ and R⁷ represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, an amino group, an acyl group, a heteroaryl group, an anionic group, a cationic group, or Q.
• Q represents a carboxy group, a substituent capable of being bonded to a biological substance, or a substituent capable of being bonded to a solid support.
• L¹ and L⁶ represent an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, or >P(=O)OR^B, L² and L⁵ represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B.
• M represents a phosphor moiety, a physiologically active substance moiety, a prodrug moiety, or a radioactive isotope-containing moiety.
• However, at least two of M's represent a phosphor moiety.
• m is an integer of 1 or more.
• X¹ to X³, L^a, L, R^A, R^B, R^E, g, and n respectively have the same meanings as X¹ to X³, L^a, L, R^A, R^B, R^E, g, and n described above.
• However, the compound represented by General Formula (II) satisfies the following definitions (α-a) and (β-a).
• Definition (α-a): The definition (α1) described above and/or the definition (α2-a) described below is satisfied.
• Definition (α2-a): At least one of L^a, L³, or L⁴ is a group having, as a substituent, a group including -(L-O)_gR^E.
• Definition (β-a): The -(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
• It is noted that R¹ to R³ respectively have the same meanings as R¹ to R³ described above.
• R⁴ and R⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group, which can be adopted as R⁴ or R⁵, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group, which can be adopted as R⁴ or R⁵, may be unsubstituted or may have a substituent, and examples of the substituent which may be contained therein include substituents in the substituent group T which will be described later. For example, a halogen atom is preferable.
• R⁴ and R⁵ are preferably a hydrogen atom or an alkyl group, and from the viewpoint of ease of synthesis, it is more preferably a hydrogen atom.
• R⁶ and R⁷ represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, an amino group, an acyl group, a heteroaryl group, an anionic group, a cationic group, or Q.
• The alkyl group, the alkenyl group, the alkynyl group, the aryl group, the alkoxy group, the amino group, the acyl group, the heteroaryl group, the anionic group, and the cationic group, which can be adopted as R⁶ or R⁷, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the aryl group, the alkoxy group, the amino group, the acyl group, the heteroaryl group, the anionic group, and the cationic group in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof.
• The alkyl group, the alkenyl group, the alkynyl group, the aryl group, the alkoxy group, the amino group, the acyl group, and the heteroaryl group, which can be adopted as R⁶ or R⁷, may be unsubstituted or may have a substituent.
• Examples of the substituent which may be contained in the alkyl group, the alkenyl group, the alkynyl group, the aryl group, the alkoxy group, the amino group, the acyl group, and the heteroaryl group, as R⁶ or R⁷, include substituents in the substituent group T which will be described later, where an alkyl group, an acyl group, an alkoxy group, an amino group, a carbamoyl group, an acylamino group, an anionic group, a cationic group, -(L-O)_gR^E, or Q, or a substituent obtained by combining two or more of these is more preferable.
• Q, which can be adopted as R⁶ or R⁷, represents a carboxy group, a substituent capable of being bonded to a biological substance, or a substituent capable of being bonded to a solid support.
• As the substituent capable of being bonded to a biological substance, the description of the substituent capable of being bonded to a biological substance described later can be applied, and as the substituent capable of being bonded to a solid support, the description of the substituent capable of being bonded to a solid support described later can be applied.
• For R⁶, the description of the substituent represented by -L⁷R^6A or -L¹³R^6A described later is preferably described, and For R⁷, the description of the substituent represented by -L⁸R^7A or -L¹²R^7A described later is preferably described.
• In the present invention, from the viewpoint that a proper hydrophilicity and a proper excluded volume effect can be provided and an excellent fluorescence intensity can be obtained, it is preferable that any one of R⁶ or R⁷ is a group including -(L-O)_gR^E, and it is more preferable that R⁷ is a group including -(L-O)_gR^E.
• L¹ and L⁶ represent an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, or >P(=O)OR^B, L² and L⁵ represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B. R^A and R^B respectively have the same meanings as R^A and R^B described above.
• The alkylene group that can constitute L¹ to L⁶ has the same meaning as the group in which one hydrogen atom is further removed from the alkyl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The alkenylene group which can be adopted as L¹ to L⁶ has the same meaning as the group in which one hydrogen atom is further removed from the alkenyl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The alkynylene group which can be adopted as L¹ to L⁶ has the same meaning as the group in which one hydrogen atom is further removed from the alkynyl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The arylene group that can constitute L¹ to L⁶ has the same meaning as the group in which one hydrogen atom is further removed from the aryl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The heteroarylene group that can constitute L¹ to L⁶ has the same meaning as the group in which one hydrogen atom is further removed from the heteroaryl group selected from the substituent group T, which is described later, and the same applies to the preferred one thereof.
• The alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L¹ to L⁶, may be an unsubstituted group or a group having a substituent.
• The substituent which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L¹ to L⁶, is not particularly limited, and it is preferably selected from a substituent group T described later. More preferred examples thereof include a halogen atom, an alkyl group, an acylamino group, a carbamoyl group, and -(L-O)_gR^E. In addition, the substituent which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L¹ to L⁶, may be substituted with a substituent selected from the substituent group T which will be described later, and it is, for example, preferably -(L-O)_gR^E.
• In addition, the number of substituents which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L¹ to L⁶, is not particularly limited as long as it can be adopted as a structure. The number thereof can be set to at least one or more, the upper limit thereof is not particularly limited, and for example, all hydrogen atoms in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group may be substituted with a substituent.
• In the linking group obtained by combining two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, which can constitute L² to L⁵, the kind of the group to be combined is not particularly limited as long as the group to be combined has a reasonable chemical structure; however, it is preferably 2 to 6 kinds and more preferably 2 to 4 kinds. It is noted that in a case of counting, as one kind, each of the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, -O-, -S-, >C=O, NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, the maximum number of kinds is 12.
• It is noted that in the linking group obtained by combining two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, which can constitute L² to L⁵, the number of groups to be combined is not particularly limited; however, examples thereof preferably include 2 to 10 groups, more preferably include 2 to 6 groups, and still more preferably 2 to 4 groups.
(i) L¹ and L⁶
• L¹ is preferably >C=O, >NR^A, an arylene group, an alkylene group, -O-, or -S-, more preferably >C=O, >NR^A, an arylene group, or an alkylene group, and still more preferably >C =O or >NR^A.
• L⁶ is preferably >C=O, >NR^A, or an arylene group, and more preferably >C=O or >NR^A.
(ii) L³ and L⁴
• L³ and L⁴ are more preferably a single bond, an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O, -, -S-, >C=O, or >NR^A, or a combination of at least one of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, or a heteroarylene group, and >C=O or >NR^A, and are more preferably a single bond, an alkylene group, >C=O, or >NR^A, or a combination of an alkylene group and >C=O or >NR^A.
• Among the above, L³ is preferably a single bond.
(iii) L² and L⁵
• L² and L⁵ are preferably a group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, and >NR^A, and are more preferably a group represented by * -L^x-L^y-**.
• L^x is a single bond or a group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, and a heteroarylene group, and L^y is a single bond, -O, -, -S-, >C=O, or >NR^A. * represents a bonding site to a carbon atom to which L¹ and L³ are bonded or a carbon atom to which L⁴ and L⁶ are bonded, and ** represents a bonding site to M. However, in a case where L^y is a single bond, L^x is a heteroarylene group or a group consisting of a group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, and an arylene group, which are located on the * side, and a heteroarylene group which is located on the ** side.
• Among the groups represented by * -L^x-L^y-**, L² and L⁵ are preferably a group in which L^y is a single bond, -S-, >C=O, or >NR^A, more preferably a group in which L^y is >C=O or >NR^A, and still more preferably a group in which L^x is an alkylene group and L^y is >C=O or >NR^A.
• It is noted that in the compound represented by General Formula (II), it suffices that the number of shortest-distance atoms in the linking chain (each linking chain of the linking chain including L² and the linking chain including L⁵) that connects M to a carbon atom to which L¹ and L^a are bonded or a carbon atom to which L⁴ and L⁶ are bonded is, for example, 1 to 60, where 1 to 40 is preferable. In a case where M is a phosphor moiety, the above-described number of shortest-distance atoms means the number of atoms that constitute the shortest chain in the linking chain that connects a conjugated structural moiety for exhibiting fluorescence in the phosphor moiety M to a carbon atom to which L¹ and L^a are bonded or a carbon atom to which L⁴ and L⁶ are bonded.
• It is noted that in the compound represented by General Formula (II), it is also preferable that a structure represented by -(CH₂-CH₂-O)_b- described later (b is also as described later) is provided at any portion of the linking chain represented by "-linking group ZZZ-L²-" in the structure represented by "the conjugated structural moiety of M - the linking group ZZZ-L²- described later" and any portion of the linking chain represented by "-linking group ZZZ-L⁵-" in the structure represented by "the conjugated structural moiety of M - the linking group ZZZ-L⁵- described later".
• In the compound represented by General Formula (II), adjacent groups may be bonded to each other to form a ring. Examples of the combination of adjacent groups which may be bonded to each other to form a ring include a combination of L¹ and L², a combination of L¹ and L^a, a combination of L² and R⁴, a combination of L⁴ and L⁵, a combination of L⁴ and L⁶, or a combination of L⁵ and R⁵.
• The above-described ring which may be formed by bonding adjacent groups to each other may be any one of an aromatic ring or an aliphatic ring or may be any one of a hydrocarbon ring or a hetero ring, and it is preferably a 5- or 6-membered ring.
• The preferred examples of the aliphatic ring include a cyclopentane ring, a cyclohexane ring, or a 5-membered ring having a carbon atom, a nitrogen atom, and X¹ to X³ as ring-constituting atoms, which is described in the structure represented by General Formula (I) described above, where a 5-membered ring having a carbon atom, a nitrogen atom, and X¹ to X³ as ring-constituting atoms, which is described in the structure represented by General Formula (I) described above, is more preferable.
• The aromatic ring is preferably a benzene ring or a nitrogen-containing aromatic heterocyclic ring, more preferably a benzene ring or a nitrogen-containing aromatic heterocyclic ring in which the ring-constituting atom is composed of a carbon atom and a nitrogen atom, and still more preferably a benzene ring or a pyridine ring.
• These rings may have a substituent, and the substituent which may be contained is not particularly limited and is selected from the substituent group T.
• The ring formed by the combination of L² and R⁴ or the combination of L⁵ and R⁵ may be any one of the above-described aliphatic ring or aromatic ring, where the above-described aliphatic ring is preferable.
• The ring formed by a combination of L¹ and L², a combination of L¹ and L^a, a combination of L⁴ and L⁵, or a combination of L⁴ and L⁶, may be any one of the above-described aliphatic ring or aromatic ring, where a 5-membered ring having a carbon atom, a nitrogen atom, and X¹ to X³ as ring-constituting atoms, which is described in the structure represented by General Formula (I) described above, or a benzene ring is preferable.
For example, the following structures surrounded by broken lines in General Formula (II)
• 

  can be set to structures including the following structures. In the following structures, * indicates a connecting portion.

  
• m is an integer of 1 or more. The upper limit value thereof is not particularly limited and can be set to, for example, an integer of 30 or less, and it is preferably an integer of 20 or less, more preferably an integer of 15 or less, and still more preferably an integer of 10 or less.
• M represents a phosphor moiety, a physiologically active substance moiety, a prodrug moiety, or a radioactive isotope-containing moiety.
• The phosphor moiety which can be adopted as M (hereinafter, also referred to as the phosphor moiety M) can be used without particular limitation as long as it is a structural moiety consisting of an organic compound that exhibits fluorescence. In addition, the phosphor moiety M may be a structural moiety in which a structural moiety consisting of an organic compound exhibiting fluorescence further has a linking group. Such a linking group is not particularly limited; however, examples thereof include a linking group ZZZ described later. For example, in the compound represented by General Formula (II), preferred examples of the compound include a compound in which the phosphor moiety M is bonded to L² or L⁵ by this linking group ZZZ.
• Examples of the phosphor moiety M include a structural moiety consisting of at least one dye of a xanthene dye, a rhodamine dye, a coumarin dye, a cyanine dye, a pyrene dye, an oxazine dye, a squarylium dye, a pyridyloxazole dye, or a pyrromethene dye, which is preferable.
• As the xanthene dye, the rhodamine dye, the coumarin dye, the cyanine dye, the pyrene dye, the oxazine dye, the squarylium dye, the pyridyloxazole dye, and the pyrromethene dye, dyes that are generally known as these dyes can be used without particular limitation.
• As one aspect, the phosphor moiety M is preferably a structural moiety consisting of a pyrromethene dye. Examples of the pyrromethene dye include a dipyrromethene boron complex. As the dipyrromethene boron complex, it is possible to use a fluorescent compound (a dipyrromethene boron complex) represented by General Formula (1) or (4) described in WO2019/230963A , or a compound (a dipyrromethene boron complex) represented by General Formula (1) described in WO2021/100814A , and the description thereof can be incorporated into the present specification by reference.
• It is noted that the incorporation is made such that the dye that constitutes the phosphor moiety M does not have a substituent capable of being bonded to a biological substance.
• In the present invention, it is preferable that all the phosphor moieties M contained in the compound are phosphor moieties of which light absorption characteristics are equivalent to each other. In the present invention, the phrase "phosphor moieties of which light absorption characteristics are equivalent to each other" means those that satisfy a relationship in which a difference in the maximum absorption wavelength between the respective phosphor moieties in the absorption spectra is within 15 nm.
• In the present invention, the compound is more preferably such that all the phosphor moieties M contained in the compound satisfies a relationship in which a difference between the maximum absorption wavelength on the lowest wavelength side and the maximum absorption wavelength on the highest wavelength side among the maximum absorption wavelengths in the absorption spectra of the respective phosphor moieties is within 15 nm.
• As a compound having two phosphor moieties in the compound, the compound that causes the FRET phenomenon is known as described above. In this compound, a difference in maximum absorption wavelength generally exceeds 15 nm between an absorption spectrum of a phosphor moiety I (an energy donor) that is excited with excitation light and an absorption spectrum of another phosphor moiety II (an energy acceptor) that receives energy from the phosphor moiety I and is quenched or emits light. In such a compound, the energy is transferred to the phosphor moiety II instead of emitting fluorescence from the phosphor moiety I, and thus the fluorescence intensity of the compound is decreased.
• On the other hand, as described above, in a case where the compound according to the embodiment of the present invention has phosphor moieties of which light absorption characteristics are equivalent to each other, the FRET phenomenon can be suppressed, and it is easy to obtain the fluorescence intensity proportional to the number of phosphor moieties.
• The chemical structures of the above-described phosphor moieties of which the light absorption characteristics are equivalent to each other are not particularly limited as long as the above-described difference in maximum absorption wavelength is satisfied, and they preferably have the same structure in terms of the main skeleton of the phosphor moiety. However, the steric conformation, chain length, and the like of the substituent may be different from each other, and in a case where an anionic group or a cationic group is contained, a counter ion thereof may be different from each other. The difference in the maximum absorption wavelength is preferably within 10 nm and more preferably within 5 nm.
• It is noted that the absorption spectrum of the phosphor moiety is a spectrum that is obtained by measuring, by using a spectrophotometer, a simple body of a phosphor constituting the phosphor moiety, which is diluted with a PBS buffer solution (phosphate-buffered saline).
• In the compound according to the embodiment of the present invention, the number of the phosphor moieties M is 2 or more. The upper limit value thereof is not particularly limited and can be set to, for example, 30 or less, and it is preferably 20 or less and more preferably 15 or less.
• As another aspect, the phosphor moiety M is preferably a structural moiety consisting of a cyanine dye, and it is more preferably a structural moiety consisting of a cyanine dye represented by General Formula (α).

  
• In the formula, R¹ to R⁴ represent an alkyl group or -(CH₂-CH₂-O)_b-R²¹. b is 1 to 50, and R²¹ represents an alkyl group.
• R¹¹ to R¹³ represent a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, or a halogen atom, where adjacent groups may be bonded to each other to form a 5-membered or 6-membered ring.
• R²² to R²⁵ and R³² to R³⁵ represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a sulfo group, a sulfamoyl group, a carboxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a carbamoyl group, an acylamino group, a nitro group, or a halogen atom.
• R⁴¹ and R⁴² represent an alkyl group or -(CH₂-CH₂-O)_b-R²¹. R²¹ and b respectively have the same meanings as R²¹ and b described above. R⁴¹ and R⁴² may be bonded to each other to form a ring.
• a is an integer of 1 to 3.
• In a case where one hydrogen atom is removed from any of R¹ to R⁴, R¹¹ to R¹³, R²² to R²⁵, R³² to R³⁵, R⁴¹, or R⁴² described above, a monovalent structural moiety is provided.
• However, the cyanine dye represented by Formula (α) is neutral.
• Depending on the length of the methine chain having a repetition number of 2a + 3, which is connected by a conjugated double bond, the cyanine dyes represented by General Formula (α) respectively have an excitation absorption wavelength in a wavelength range of 520 to 600 nm (in the vicinity of 585 nm) in a case of a = 1, in a wavelength range of 620 to 700 nm (in the vicinity of 685 nm) in a case of a = 2, and in a wavelength range of 740 to 830 nm (in the vicinity of 785 nm) in a case of a = 3. As a result, each of the compounds according to the embodiment of the present invention which has, as the phosphor moiety M, a structural moiety consisting of a cyanine dye represented by General Formula (α) can be used as a compound exhibiting an excellent fluorescence intensity, in the fluorescence labeling in which a light source having any wavelength in a wavelength range of about 500 to 800 nm (for example, in the vicinity of 600 nm, in the vicinity of 700 nm, or in the vicinity of 800 nm) matching with the absorption excitation wavelength of the compound is used as an excitation light source.
• In multicolor WB, a plurality of luminescence colors are detected in the range from the visible range to the near infrared range. As a result, it is necessary to select wavelengths so that the absorption and luminescence waveforms of a plurality of dyes have a suitable wavelength relationship so that crosstalk does not occur due to mutual interference in a case where the dyes are excited to emit light. Ideally, it should be adjusted so that only one dye emits light at one excitation light and the other dyes do not emit light. From this point of view, two kinds of excitation light sources having wavelengths separated to some extent, for example, in the vicinity of 700 nm and in the vicinity of 800 nm, are used for luminescence in the near infrared range of the multicolor WB.
• As compared with the detection by visible light excitation, the fluorescence detection by near-infrared light excitation can suppress the autofluorescence of the membrane, that is, the background fluorescence, and thus it is easy to increase the signal to noise ratio (the S/N ratio) and it is possible to detect a target protein with high sensitivity. As a result, in recent years, there has been an increasing need for fluorescence detection WB using luminescence in the near infrared range in the analytical research on the trace amount of proteins.
• However, in the near infrared range, the fluorescence quantum yield of the fluorescent dye is generally low, and thus it is difficult to obtain a high signal amount. Among the compounds according to the embodiment of the present invention which has, as the phosphor moiety M, a structural moiety consisting of a cyanine dye represented by General Formula (α), the compound in which a = 2 or 3 can be used as a compound that exhibits an excellent fluorescence intensity even in the multicolor WB having the above-described two kinds of excitation light sources in the vicinity of 700 nm and in the vicinity of 800 nm, and in particular, it can exhibit an excellent fluorescence intensity even with respect to a request for observing and detecting proteins with higher sensitivity, as compared with the fluorescence labeling using cyanine dyes in the related art.
(i) R¹ to R⁴
• R¹ to R⁴ represent an alkyl group or -(CH₂-CH₂-O)_b-R²¹.
• The alkyl group which can be adopted as R¹ to R⁴ has the same meaning as the alkyl group in the substituent group T which will be described later.
• The unsubstituted alkyl group preferably has 1 to 6 carbon atoms, more preferably has 1 to 4 carbon atoms, and still more preferably has 1 or 2 carbon atoms.
• In a case where the alkyl group has a substituent, the alkyl group moiety of the alkyl group having a substituent preferably has 1 to 10 carbon atoms, more preferably has 1 to 8 carbon atoms, still more preferably has 2 to 6 carbon atoms, and particularly preferably has 2 to 5 carbon atoms. In addition, the number of atoms that constitute the longest chain of the alkyl group having a substituent is preferably 3 to 35, more preferably 3 to 25, still more preferably 3 to 15, and particularly preferably 3 to 11.
• In the present invention, the "number of carbon atoms of the alkyl group moiety of the alkyl group having a substituent" means the number of carbon atoms excluding the substituent moiety contained in the alkyl group.
• In the present invention, the "number of atoms that constitute the longest chain of the alkyl group having a substituent" means the number of atoms including the substituent moiety (that is, the number of atoms obtained by subtracting the number of atoms of the molecular chain that does not constitute the longest chain, from the number of total atoms). It is noted that in a case where a substituent having a dissociative hydrogen atom such as a sulfo group or a carboxy group constitutes the longest chain, the calculation is carried out including the hydrogen atom regardless of the presence or absence of dissociation. In addition, the number of atoms in the substituent moiety capable of being bonded to a biological substance described later is not included.
• Examples of the substituent which may be contained in the alkyl group which can be adopted as R¹ to R⁴ include an alkoxy group, a carboxy group, an alkoxycarbonyl group, an acyloxy group, a carbonyl group, an acylamino group, a sulfo group, a phosphono group, and -(CH₂-CH₂-O)_b-R²¹, as well as a group consisting of a combination of these substituents.
• The alkyl group having a substituent, which can be adopted as R¹ to R⁴, is not particularly limited as long as it is the above-described alkyl group having a substituent.
• The alkyl group which can be adopted as R¹ to R⁴ is preferably an unsubstituted alkyl group.
(-(CH₂-CH₂-O)_b-R²¹)
• In -(CH₂-CH₂-O)_b-R²¹ which can be adopted as R¹ to R⁴, b is 1 to 50, and R²¹ represents an alkyl group.
• b means an average repetition number (simply, also referred to as a repetition number), and it is preferably 1 to 24, more preferably 1 to 12, still more preferably 1 to 10, particularly preferably 4 to 10, and most preferably 4 to 8.
• The average repetition number can be calculated from the average integrated value obtained by subjecting a compound to ¹H-NMR measurement. The average repetition number defined in the present invention means a number that is obtained by rounding off the first decimal place of the average repetition number calculated according to the above method.
• To the alkyl group as R²¹, the description of the alkyl group which can be adopted as R¹ to R⁴ described above can be applied.
• The -(CH₂-CH₂-O)_b-R²¹ which can be adopted as R¹ to R⁴ and -(CH₂-CH₂-O)_b-R²¹ which can be adopted as a substituent by an alkyl group as R¹ to R⁴ are preferably an alkyl group of -(CH₂-CH₂-O_b-unsubstituted.
• From the viewpoint of further improving the fluorescence intensity of the fluorescent dye itself, it is preferable that at least one of R¹, ..., or R⁴ includes a structure represented by -(CH₂-CH₂-O)_b-, and it is more preferable at least one of R¹ or R² and at least one of R³ or R⁴ include a structure represented by -(CH₂-CH₂-O)_b-.
• It is still more preferable that the entire phosphor moiety M in the compound according to the embodiment of the present invention is a structural moiety consisting of a cyanine dye represented by General Formula (α), where at least one of R¹ or R² and at least one of R³ or R⁴ includes a structure represented by -(CH₂-CH₂-O)_b-.
• It is preferable that the structure represented by -(CH₂-CH₂-O)_b- is introduced by employing -(CH₂-CH₂-O)_b -R²¹ as R¹ to R⁴.
• The b in -(CH₂-CH₂-O)_b- described above has the same meaning as the b in -(CH₂-CH₂-O)_b-R²¹ described above.
• Since the substituents of R¹ to R⁴ protrude in a direction perpendicular to the cyanine dye skeleton (plane), it is presumed that in a case of including a structure represented by -(CH₂-CH₂-O)_b- as this substituent, the fused ring portion is difficult to undergo the π-π interaction (the effect of suppressing the association is strengthened), and thus the decrease in the fluorescence intensity due to the association can be suppressed.
(ii) R¹¹ to R¹³
• R¹¹ to R¹³ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, or a halogen atom. Adjacent groups may be bonded to each other to form a 5- or 6-membered ring.
• The alkyl group, the alkoxy group, the aryloxy group, the alkylthio group, the arylthio group, the amino group, and the halogen atom, which can be adopted as R¹¹ to R¹³, respectively have the same meanings as the alkyl group, the alkoxy group, the aryloxy group, the alkylthio group, the arylthio group, the amino group, and the halogen atom in the substituent group T described later, and the same applies to the preferred ranges thereof.
• Examples of the substituent which may be contained in the alkyl group, the alkoxy group, the aryloxy group, the alkylthio group, the arylthio group, and the amino group, as R¹¹ to R¹³, include the substituents in the substituent group T described below.
• Among R¹¹ to R¹³, the 5- or 6-membered ring formed by bonding adjacent groups to each other may be either aromatic or aliphatic, and it is preferably aliphatic. In addition, it is preferable to form a 6-membered ring. The number of the above-described 5- or 6-membered rings in the compound is not particularly limited; however, it is preferably 1 or 2 and more preferably 1.
• In a case of taking a case of a = 3 as an example, preferred examples of the structure having a ring formed by bonding adjacent groups among R¹¹ to R¹³ include the following structures. It is noted that in the following examples, R¹¹ to R¹³ that do not form a ring structure are a hydrogen atom, and the ring structure is described as a structure that does not have a substituent, which are not limited thereto. It is noted that, hereinafter, the structure beyond the wavy line will be omitted.

  

  
• R¹¹ and R¹³ possessed by the carbon atom bonded to the indolenine ring are preferably a hydrogen atom.
• R¹², and R¹³ other than those described are preferably a hydrogen atom or an alkyl group.
• Among R¹¹ to R¹³, adjacent groups in R¹² and R¹³ other than R¹¹ and R¹³ possessed by the carbon atom bonded to the indolenine ring (that is, adjacent groups of R¹³ and R¹² other than R¹³ possessed by the carbon atom bonded to the indolenine ring) are preferably bonded to each other to form a 5- or 6-membered ring and more preferably to form a 6-membered ring. In addition, it is preferable that the 5- or 6-membered ring is formed at the central portion of the bond that connects the indoline ring and the indolenine ring. The ring formed in the central portion of the bond connecting the indoline ring and the indolenine ring means a ring containing carbon atoms as ring-constituting atoms so that the numbers of bonded atoms from the indoline ring and the indolenine ring are the same.
• In a case where one hydrogen atom is removed from any of R¹ to R⁴, R¹¹ to R¹³, R²² to R²⁵, R³² to R³⁵, R⁴¹, or R⁴² described above, the phosphor moiety M is a monovalent structural moiety.
• Specifically, a monovalent structural moiety is provided in a case where one hydrogen atom is removed from a substituent which can be adopted as R¹ to R⁴, R¹¹ to R¹³, R²² to R²⁵, R³² to R³⁵, R⁴¹, or R⁴², or a hydrogen atom which can be adopted as R¹¹ to R¹³, R²² to R²⁵, or R³² to R³⁵ is removed to provide a monovalent structural moiety which has a bonding site on the carbon atom to which R¹¹ to R¹³, R²² to R²⁵, or R³² to R³⁵ has been bonded.
• Among the above, it is preferable that the phosphor moiety M is to be a monovalent structural moiety by removing one hydrogen atom from the ring formed by the bonding of R⁴¹ and R⁴² described above or is to be a monovalent structural moiety by removing one hydrogen atom from a substituent which can be adopted as R¹² (preferably R¹² on the carbon atom at which the numbers of bonded atoms from the indoline ring and the indolenine ring are the same).
(iii) R²² to R²⁵ and R³² to R³⁵
• R²² to R²⁵ and R³² to R³⁵ represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a sulfo group, a sulfamoyl group, a carboxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a carbamoyl group, an acylamino group, a nitro group, or a halogen atom. Regarding this R²² to R²⁵ and R³² to R³⁵, adjacent groups may be bonded to each other to form a fused ring.
• The alkyl group, the alkoxy group, the aryl group, the sulfo group, the sulfamoyl group, the carboxy group, the alkoxycarbonyl group, the aryloxycarbonyl group, the acyloxy group, the carbamoyl group, the acylamino group, the nitro group, and the halogen atom, which can be adopted as R²² to R²⁵ and R³² to R³⁵, respectively have the same meanings as the alkyl group, the alkoxy group, the aryl group, the sulfo group, the sulfamoyl group, the carboxy group, the alkoxycarbonyl group, the aryloxycarbonyl group, the acyloxy group, the carbamoyl group, the acylamino group, the nitro group, and the halogen atom in the substituent group T which will be described later.
• The fused ring formed by bonding adjacent groups among R²² to R²⁵ and R³² to R³⁵ to each other is not particularly limited. However, examples thereof include a naphthalene ring (a naphthalene ring that is formed together with a benzene ring to which R²² to R²⁵ are bonded or a benzene ring to which R³² to R³⁵ are bonded in a case where adjacent groups are bonded to each other to form the benzene ring). From the viewpoint of suppressing association, it is preferable that adjacent groups among R²² to R²⁵ and R³² to R³⁵ are not bonded to each other and do not form a fused ring.
• From the viewpoint of improving water solubility and suppressing association, it is preferable that at least one of R²², ..., or R²⁵ and at least one of R³², ..., or R³⁵ have a hydrophilic group, and it is more preferable that at least one hydrophilic group is contained per the number of rings of one, to which R²² to R²⁵ are bonded and rings to which R³² to R³⁵ are bonded. For example, in a case where adjacent groups among R²² to R²⁵ and R³² to R³⁵ are bonded to each other to form a naphthalene ring as a fused ring, the number of rings to which R²² to R²⁵ are bonded is two, and the number of rings to which R³² to R³⁵ are bonded to each other is two, which means that it is more preferable that at least two of R²² to R²⁵ and at least two of R³² to R³⁵ have a hydrophilic group. The upper limit value thereof is not particularly limited as long as it is allowed in terms of structure, and it can be appropriately adjusted in accordance with the number of hydrophilic groups in the compound as a whole, which will be described later.
• The hydrophilic group is not particularly limited; however, examples thereof include an alkoxy group having a substituent, a carboxy group, a sulfo group, and a phosphono group, where a sulfo group is preferable.
• R²² to R²⁵ and R³² to R³⁵ are preferably a hydrogen atom, an alkyl group, a sulfo group, a nitro group, or a halogen atom, more preferably a hydrogen atom, an alkyl group, a sulfo group, or a halogen atom, and still more preferably a hydrogen atom, an alkyl group, or a sulfo group.
(iv) R⁴¹ and R⁴²
• R⁴¹ and R⁴² represent an alkyl group or -(CH₂-CH₂-O)_b-R²¹. R²¹ and b respectively have the same meanings as R²¹ and b described above.
• Examples of the substituent which may be contained in the alkyl groups as R⁴¹ and R⁴² include an alkoxy group, a carboxy group, an alkoxycarbonyl group, an acyloxy group, a carbamoyl group, an acylamino group, a sulfo group, and a phosphono group, as well as a group consisting of a combination of these substituents.
• The alkyl group which can be adopted as R⁴¹ and R⁴² has the same meaning as the alkyl group in the substituent group T which will be described later.
• The unsubstituted alkyl group preferably has 1 to 6 carbon atoms, more preferably has 1 to 4 carbon atoms, and still more preferably has 1 to 3 carbon atoms.
• The alkyl group moiety of the alkyl group having a substituent preferably has 1 to 10 carbon atoms, more preferably has 1 to 8 carbon atoms, still more preferably has 1 to 7 carbon atoms, even still more preferably has 1 to 6 carbon atoms, and even further still more preferably has 1 to 5 carbon atoms. In addition, the number of atoms that constitute the longest chain of the alkyl group having a substituent is preferably 3 to 14, more preferably 3 to 12, and still more preferably 3 to 10.
• The alkyl group having a substituent, which can be adopted as R⁴¹ and R⁴², is preferably an alkyl group having, as a substituent, at least one of an alkoxy group, a carboxy group, a sulfo group, or a phosphono group, and more preferably an alkyl group having, as a substituent, at least one of a carboxy group or a sulfo group, from the viewpoint of further improving water solubility. It is noted that it may be an alkyl group having a substituent consisting of a combination of the above-described preferred substituents (the alkoxy group, the carboxy group, the sulfo group, and the phosphono group) and a group other than these substituents.
• In addition, the form of the alkyl group having a substituent, which can be adopted by R¹ to R⁴, can be also preferably applied.
• To -(CH₂-CH₂-O)_b-R²¹ which can be adopted as R⁴¹ and R⁴², the description of -(CH₂-CH₂-O)_b-R²¹ in R¹ to R⁴ can be preferably applied.
• R⁴¹ and R⁴² may be bonded to each other to form a ring.
• Among the cyanine dyes represented by General Formula (α), preferred examples of the structure in which R⁴¹ and R⁴² are bonded to each other to form a ring include a cyanine dye represented by General Formula (β).

  
• In the formula, L^x to L^y represent an alkylene group or -(CH₂-CH₂-O)_b-alkylene-*. * represents a bonding position to U.
• The linking group U represents a divalent linking group having 1 to 100 atoms.
• R¹ to R⁴, R¹¹ to R¹³, R²² to R²⁵, R³² to R³⁵, b, and a respectively have the same meanings as R¹ to R⁴, R¹¹ to R¹³, R²² to R²⁵, R³² to R³⁵, b, and a in General Formula (α), and the same also applies to the preferred ranges thereof unless otherwise specified.
• At least one of R¹, R², R³, R⁴, L^x, or U includes a structure represented by-(CH₂-CH₂-O)_b-. m has the same meaning as m described above.
• However, the cyanine dye represented by Formula (β) is neutral.
• The alkylene group which can be adopted as L^x and L^y corresponds to an alkylene group obtained by removing one hydrogen atom or one substituent from an alkyl group having a substituent which can be adopted as R⁴¹ and R⁴².
• For the number of carbon atoms of the alkylene group moiety of the alkylene group which can be adopted as L^x to L^y, the description of the number of carbon atoms of the alkyl group moiety of the alkyl group having a substituent, as R⁴¹ and R⁴², can be preferably applied.
• The -(CH₂-CH₂-O)_b-alkylene-* which can be adopted as L^x and L^y corresponds to -(CH₂-CH₂-O)_b-alkylene obtained by removing one hydrogen atom or one substituent from the alkyl group as R²¹, among the -(CH₂-CH₂-O)_b-R²¹ which can be adopted as R⁴¹ and R⁴² (R²¹ represents an alkyl group having a substituent).
• In the -(CH₂-CH₂-O)_b-alkylene-* which can be adopted as L^x and L^y, b is preferably 1 to 10 and more preferably 1 to 8, and as the number of carbon atoms of the alkylene group moiety, the description of the number of carbon atoms of the alkyl group moiety of the alkyl group having a substituent in R⁴¹ to R⁴² can be preferably applied.
• From the viewpoint of further improving the fluorescence intensity, it is preferable that both L^x and L^y include a structure represented by -(CH₂-CH₂-O)_b-.
• The total number of atoms constituting the linking group U is 1 to 100, and it is preferably 10 to 90, more preferably 20 to 90, and still more preferably 30 to 80.
• The linking group U is preferably a divalent linking group formed by bonding three or more selected from an alkylene group, -O-, -NR⁵⁰-, -COO-, -CONR⁵⁰-, and -SO₂NR⁵⁰-. R⁵⁰ represents a hydrogen atom or an alkyl group.
• The number of carbon atoms in the alkylene moiety of the alkylene group which can be adopted as the linking group U is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 7, particularly preferably 1 to 6, and most preferably 1 to 5.
• In the present invention, "the number of carbon atoms in the alkylene moiety of the alkylene group" means the number of carbon atoms excluding the substituent moiety contained in the alkylene group.
• As the alkyl group which can be adopted as R⁵⁰, the description of the alkyl group as R¹ to R⁴ can be preferably applied.
• R⁵⁰ is preferably a hydrogen atom.
• The number of the above-described alkylene group, -O-, -NR⁵⁰-, -COO-, -CONR⁵⁰-, and -SO₂NR⁵⁰-, constituting the linking group U, is preferably 3 to 11, more preferably 3 to 7, still more preferably 3 to 5, and particularly preferably 3.
• In the linking group U, the connecting portion to L^x to L^y is preferably -O-, -NR⁵⁰-, -COO-, -CONR⁵⁰-, or -SO₂NR⁵⁰-. That is, the linking group U is preferably bonded to the alkylene groups of L^x to L^y through -O-, -NR⁵⁰-, -COO-, -CONR⁵⁰-, or -SO₂NR⁵⁰-, which constitutes the linking group U. In the linking group U, it is more preferable that connecting portions to L^x to L^y are -O-, -NR⁵⁰-, -COO-, -CONR⁵⁰-, or -SO₂NR⁵⁰-, where the linking group U is a divalent linking group in which the connecting portions are connected to each other through an alkylene group.
• It is preferable that the linking group U is to be a monovalent structural moiety, that is, a phosphor moiety M, by removing one hydrogen atom therefrom. In the linking group U, examples of the position where one hydrogen atom is removed include an alkylene group and an alkyl group as R⁵⁰, where an alkylene group is preferable.
• In a case where in the linking group U, one hydrogen atom is removed in the alkylene group or the alkyl group as R⁵⁰, one hydrogen atom may be directly removed from the alkylene group or the alkyl group as R⁵⁰, and the linking group ZZZ may be bonded to the alkylene group or the alkyl group as R⁵⁰, thereby the linking group ZZZ serving as a bonding site.
• Examples of the linking group ZZZ include an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR⁶⁰, >S=O, >S(=O)₂, >P(=O)OR⁷⁰, -COO-, -CONR⁶⁰-, and -(CH₂-CH₂-O)_p-, as well as a group consisting of a combination of these substituents. The number of those to be combined is not particularly limited; however, it can be set to, for example, 2 to 20, and it is preferably 2 to 7 and more preferably 2 to 5.
• R⁶⁰ and R⁷⁰ are a hydrogen atom or an alkyl group and are preferably a hydrogen atom. To the alkyl group which can be adopted as R⁶⁰ or R⁷⁰, the description of the alkyl group as R⁵⁰ can be preferably applied.
• p represents the repetition number, and it is preferably 1 to 10, more preferably 1 to 8, and still more preferably 1 to 4.
(v) a
• a is an integer of 1 to 3, where it is preferably an integer of 2 or 3.
• In the cyanine dye represented by General Formula (α), it is preferable that at least one of R¹, R², R³, R⁴, R⁴¹, or R⁴² includes a structure represented by -(CH₂-CH₂-O)_b-. b has the same meaning as b described above. It is conceived that this makes it possible for the compound according to the embodiment of the present invention, which has a structural moiety consisting of a cyanine dye represented by General Formula (α), to have a proper hydrophilicity and a proper excluded volume effect, whereby a labeled biological substance to be obtained can exhibit an excellent fluorescence intensity.
• In addition, from the viewpoint that sufficient hydrophilicity is imparted as the compound according to the embodiment of the present invention, the cyanine dye represented by General Formula (α) is such that the number of hydrophilic groups per one molecule of the cyanine dye represented by General Formula (α) is preferably 2 or more, more preferably 2 to 8, still more preferably 2 to 6, and particularly preferably 3 to 6.
• To the hydrophilic group, the description of the hydrophilic group which can be adopted by R²² to R²⁵ and R³² to R³⁵ described above can be applied.
• The position of the hydrophilic group is not particularly limited unless specified otherwise, and examples of the group having the hydrophilic group preferably include R¹¹ to R¹³, R²² to R²⁵, R³² to R³⁵, R⁴¹, or R⁴².
• It is noted that in the structure represented by General Formula (α) or (β), one hydrogen atom may be removed from any substituent to provide a monovalent structural moiety (the phosphor moiety M); however, it is preferable that, for example, one hydrogen atom is removed from the linking group U to provide a monovalent structural moiety, or one hydrogen atom is removed from a substituent, which can be adopted as R¹² (preferably R¹² on the carbon atom at which the numbers of bonded atoms from the indoline ring and the indolenine ring are the same), to provide a monovalent structural moiety.
• The physiologically active substance moiety which can be adopted as M can be used without particular limitation as long as it is a structural moiety consisting of a physiologically active substance. Examples of the physiologically active substance include a vitamin, a coenzyme, a hormone, an antibiotic, a neurotransmitter, and a cytokine. More specific examples thereof are calicheamicin, doxorubicin, daunorubicin, mitomycin C, bleomycin, cyclocytidine, vincristine, vinblastine, methotrexate, cisplatin or a derivative thereof, auristatin or a derivative thereof, maytansine or a derivative thereof, taxol or a derivative thereof, and camptothecin or a derivative thereof, which are described in paragraph [0095] of JP2021-020956A , and the description of paragraphs [0095] to [0099] of JP2021-020956A can be applied thereto.
• The prodrug moiety which can be adopted as M can be used without particular limitation as long as it is a structural moiety consisting of a compound that is metabolized in vivo to be changed to a physiologically active substance. To the prodrug, for example, the description (a prodrug form of 2-pyrrolinodoxorubicin) in paragraph [0003] of JP2020-105187A can be applied.
• The radioactive isotope-containing moiety which can be adopted as M can be used without particular limitation as long as it is a structural moiety containing a radioactive isotope that is capable of being used in the medical field. Examples of the radioactive isotope include iodine 131, indium 111, yttrium 90, lutetium 177, and copper 64, which are not limited thereto. The description of paragraph [0225] of JP2021-11483A can be applied thereto. Examples of the structural moiety containing a radioactive isotope include a structural moiety in which the radioactive isotope is bonded or coordinated to a nitrogen atom of an amino group or a tertiary amine, a sulfanyl group, an aryl group, a heteroaryl group, or the like. Examples of the structural moiety in which a nitrogen atom of a tertiary amine is coordinated to the radioactive isotope) include a structural moiety in which 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or the like is coordinated to the radioactive isotope to form a complex, and examples of the structural moiety in which a sulfanyl group is coordinated to the radioactive isotope include a structural moiety consisting of a complex such as copper (II) diacetylbis(N(4)-methylthiosemicarbazonate).
<Compound represented by General Formula (III)>
• The compound represented by General Formula (II) is preferably represented by General Formula (III).

  
• In the formula, Y¹ to Y³, Z¹ to Z³, and W¹ to W³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group.
• LL¹ and LL² represent a single bond or a linking group obtained by combining one or two of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B.
• s, t, and u are an integer of 0 or more.
• R⁴ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, L, R^A, R^B, R^E, g, n, and m respectively have the same meanings as R⁴ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, L, R^A, R^B, R^E, g, n, and m described above.
• However, the compound represented by General Formula (III) satisfies the following definitions (α-b) and (β-b).
• Definition (α-b): The definition (α1) described above and/or the definition (α2-b) described below is satisfied.
• Definition (α2-b): At least one of Y¹, Y², Y³, Z¹, Z², Z³, W¹, W², or W³ is a group including -(L-O)_gR^E.
• Definition (β-b): The -(L-O)_gR^E in R¹ to R³, Y¹ to Y³, Z¹ to Z³, and W¹ to W³, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
• It is noted that R¹ to R³ respectively have the same meanings as R¹ to R³ described above.
• However, the structure parenthesized by s, t, or u is not allowed to be the structure represented by General Formula (I) described above. That is, Y¹ is not allowed to be bonded to W¹ or Z¹, Y² is not allowed to be bonded to W² or Z², or Y³ is not allowed to be bonded to W³ or Z³ to form a structure represented by General Formula (I).
• Y¹ to Y³, Z¹ to Z³, and W¹ to W³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group, which can be adopted as Y¹ to Y³, Z¹ to Z³, or W¹ to W³, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group, which can be adopted as Y¹ to Y³, Z¹ to Z³, or W¹ to W³, may be unsubstituted or may have a substituent, and examples of the substituent which may be contained therein include substituents in the substituent group T which will be described later. For example, a halogen atom, an acylamino group, a carbamoyl group, or -(L-O)_gR^E is preferable.
• In addition, the substituent which may be contained in the above-described alkyl group, alkenyl group, alkynyl group, acyl group, amino group, alkoxy group, aryl group, and heteroaryl group, which can constitute Y¹ to Y³, Z¹ to Z³, or W¹ to W³, may be substituted with a substituent selected from the substituent group T which will be described later, and for example, -(L-O)_gR^E is preferable.
• Y¹ to Y³ are preferably a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, and more preferably a hydrogen atom.
• W¹ to W³ are preferably a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, and more preferably a hydrogen atom.
• Z¹ to Z³ are preferably an alkyl group, an aryl group, or a heteroaryl group, and more preferably an alkyl group.
• In order to suppress the interaction between the structures represented by General Formula (I), the compound represented by General Formula (III) preferably has a group having a steric repulsive action, and from this viewpoint, at least one of Y¹, Y², Y³, Z¹, Z², Z³, W¹, W², or W³ is preferably a group including -(L-O)_gR^E, and more preferably an alkyl group including -(L-O)_tR^E.
• Here, the description that "at least one of Y¹, Y², Y³, Z¹, Z², Z³, W¹, W², or W³ is a group including -(L-O)_gR^E" means that at least one of the following condition (Z1), (Z2), or (Z3) is satisfied.
• Condition (Z1): The s is an integer of 1 or more, and at least one of the Y¹, the Z¹, or the W¹ is a group including -(L-O)_gR^E.
• Condition (Z2): The t is an integer of 1 or more, and at least one of the Y², the Z², or the W² is a group including -(L-O)_gR^E.
• Condition (Z3): The u is an integer of 1 or more, and at least one of the Y³, the Z³, or the W³ is a group including -(L-O)_gR^E.
• In addition, the description that "at least one of Y¹, Y², Y³, Z¹, Z², Z³, W¹, W², or W³ is an alkyl group including -(L-O)_gR^E" means that in a case where "a group including -(L-O)_gR^E" in the conditions (Z1) to (Z3) is read as "an alkyl group including -(L-O)_gR^E", at least one of the condition (Z1), (Z2), or (Z3) is satisfied.
• LL¹ and LL² represent a single bond or a linking group obtained by combining one or two of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B. R^A and R^B respectively have the same meanings as R^A and R^B described above.
• To the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute LL¹ and LL², the description of the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L^a or L^b described above, can be preferably applied.
• LL¹ and LL² are preferably >C=O, >NR^A, an alkylene group, an arylene group, or a heteroarylene group, and more preferably >C=O or NR^A. It is noted that R^A is preferably a hydrogen atom.
• s, t, and u are an integer of 0 or more.
• The upper limit value of each of s, t, and u is not particularly limited and can be set to, for example, 20 or less, and it is preferably 10 or less and more preferably 5 or less. Among the above, s, t, and u are preferably an integer of 0 or 1.
• It is noted that in a case where a structure can be classified into both a structure parenthesized by t and a structure parenthesized by u, it is preferentially classified into a structure parenthesized by u.
<Compound represented by General Formula (IV)>
• The compound represented by General Formula (III) is preferably represented by General Formula (IV).

  
• In the formula, R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q. However, at least one of R^6A or R^7A represents Q.
• L⁷ and L⁸ represent a single bond or a linking group obtained by combining one or two of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B.
• Y⁴ and Y⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group.
• R⁴, R⁵, L², L⁵, X¹ to X³, Y¹ to Y³, Z¹ to Z³, W¹ to W³, M, Q, R^A, R^B, n, m, s, t, and u respectively have the same meanings as R⁴, R⁵, L², L⁵, X¹ to X³, Y¹ to Y³, Z¹ to Z³, W¹ to W³, M, Q, R^A, R^B, n, m, s, t, and u described above.
• R^6A or R^7A and L⁷ or L⁸ are each determined such that R^6A or R^7A is an unsubstituted group and L⁷ or L⁸ is the longest group. However, in a case where the group represented by -L⁷R^6A or -L⁸R^7A has an anionic group, a cationic group, or Q, it is determined such that the anionic group, the cationic group, or Q, which is located on the most terminal side (the R^6A side in -L⁷R^6A or the R^7A side in -L⁸R^7A), is R^6A or R^7A.
• R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q. However, at least one of R^6A or R^7A represents Q.
• The alkyl group, the alkenyl group, the alkynyl group, the aryl group, the alkoxy group, the heteroaryl group, the amino group, the acyl group, the anionic group, and the cationic group, which can be adopted as R^6A and R^7A, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the aryl group, the alkoxy group, the heteroaryl group, the amino group, the acyl group, the anionic group, and the cationic group in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof. However, all the groups are unsubstituted groups.
• Q which can be adopted as R^6A and R^7A has the same meaning as Q described above, and the same applies to the preferred range thereof.
• R^6A is preferably an alkyl group, a sulfanyl group, an aryl group, a heteroaryl group, or Q, and more preferably an alkyl group or Q.
• R^7A is preferably an alkyl group, a sulfanyl group, an aryl group, a heteroaryl group, or Q, and more preferably an alkyl group or Q.
• L⁷ and L⁸ represent a single bond or a linking group obtained by combining one or two of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B. R^A and R^B respectively have the same meanings as R^A and R^B described above.
• To the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L⁷ or L⁸, the description of the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L¹ to L⁶ described above, can be preferably applied.
• The substituent which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L⁷ or L⁸, is not particularly limited, and it is preferably selected from a substituent group T described later. More preferred examples thereof include a halogen atom, an aryl group, an alkyl group, an acylamino group, a carbamoyl group, and -(L-O)_gR^E. In addition, the substituent which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L⁷ or L⁸, may be substituted with a substituent selected from the substituent group T which will be described later, and it is, for example, preferably -(L-O)_gR^E.
• In addition, the number of substituents which may be contained in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group, which can constitute L⁷ or L⁸, is not particularly limited as long as it can be adopted as a structure. The number thereof can be set to at least one or more, the upper limit thereof is not particularly limited, and for example, all hydrogen atoms in the alkylene group, the alkenylene group, the alkynylene group, the arylene group, and the heteroarylene group may be substituted with a substituent.
• In the present invention, from the viewpoint of ease of synthesis, it is preferable that any one of L⁷ or L⁸ preferably includes a structure represented by -(L-O)_g-, and it is more preferable that L⁸ includes a structure represented by -(L-O)_g-. L and g respectively have the same meanings as L and g in the polyalkyleneoxy group which will be described later.
• L⁷ is more preferably a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and it is still more preferably an alkylene group, -O-, >C=O, >NR^A, a group in which -NR^A-alkylene group is bonded to a right side of a repeating unit (preferably having the repetition number of 1 to 20) represented by -[NR^A-alkylene-C(=O)]-, -NR^A-(L-O)_g-alkylene, or -C(=O)-(L-O)_g- alkylene.
• L⁸ is more preferably a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and it is still more preferably an alkylene group, -O-, >C=O, >NR^A, a group in which -NR^A-alkylene group is bonded to a right side of a repeating unit (preferably having the repetition number of 1 to 20) represented by -[NR^A-alkylene-C(=O)]-, -NR^A-(L-O)_g-alkylene, or -C(=O)-(L-O)_g- alkylene.
• Y⁴ and Y⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group.
• The alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group, which can be adopted as Y⁴ or Y⁵, respectively have the same meanings as the alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group in the substituent group T which will be described later, and the same also applies to the preferred ranges thereof.
• It is noted that all the alkyl group, the alkenyl group, the alkynyl group, the acyl group, the amino group, the alkoxy group, the aryl group, and the heteroaryl group, which can be adopted as Y⁴ or Y⁵, may be an unsubstituted group or a group having a substituent.
• Y⁴ and Y⁵ are preferably a hydrogen atom or an alkyl group and more preferably a hydrogen atom.
<Compound represented by General Formula (V)>
• The compound represented by General Formula (II) is also preferably represented by General Formula (V). The compound represented by General Formula (V) corresponds to a compound in which L¹ and L⁴ are >NH, L^a and L⁶ are >C=O, L³ is a single bond, R⁴ and R⁵ are a hydrogen atom, and L¹ and L², and L⁴ and L⁵ are respectively bonded to each other to form a specific 5-membered ring in the compound represented by General Formula (II).

  
• In the formula, X⁴ to X⁹ represent -O-, -S-, >NR¹⁰¹, or >CR¹⁰²R¹⁰³.
• However, one of X⁴, X⁵, or X⁶ is a carbon atom or a nitrogen atom, which has -L¹⁰-M as any one of R¹⁰¹, R¹⁰², or R¹⁰³, and one of X⁷, X⁸, or X⁹ is a carbon atom or a nitrogen atom, which has -L¹¹-M as any one of R¹⁰¹, R¹⁰², or R¹⁰³.
• R¹⁰¹ to R¹⁰³, which are neither -L¹⁰-M nor -L¹¹-M, represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an acyl group, -NR⁸R⁹, -OR¹⁰, or an anionic group.
• L¹⁰ and L¹¹ represent a single bond or a divalent linking group.
• R⁶ to R¹⁰, X¹ to X³, M, n, and m respectively have the same meanings as R⁶ to R¹⁰, X¹ to X³, M, n, and m in General Formula (II) described above.
• However, a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E. R¹ to R³ which include the -(L-O)_gR^E are not bonded to at least any one of a phosphor or a biological substance. To the description of this definition, the description of the definition (α1) in the descriptions pertaining to the definitions (α) and (β) in General Formula (I) described above, and the description in the definition (β), which corresponds to that in the definition (α1) can be applied.
• It is noted that R¹ to R³ respectively have the same meanings as R¹ to R³ described above.
• To X⁴ to X⁶, the description of X¹ to X³ in General Formula (I) described above can be applied unless otherwise specified, except that one of X⁴, X⁵, or X⁶ is >NR¹⁰¹ or >CR¹⁰²R¹⁰³, where R¹⁰¹ is -L¹⁰-M in a case where one of X⁴, X⁵, or X⁶ is >NR¹⁰¹ and R¹⁰² or R¹⁰³ is -L¹⁰-M in a case where one of X⁴, X⁵, or X⁶ is >CR¹⁰²R¹⁰³.
• In addition, the description of X¹ to X³ in General Formula (I) described above can be applied to X⁷ to X⁹ unless otherwise specified, except that one of X⁷, X⁸, or X⁹ is >NR¹⁰¹ or >CR¹⁰²R¹⁰³, where R¹⁰¹ is -L¹¹-M in a case where one of X⁷, X⁸, or X⁹ is >NR¹⁰¹ or R¹⁰² or R¹⁰³ is -L¹⁰-M in a case where one of X⁷, X⁸, or X⁹ is >CR¹⁰²R¹⁰³.
• That is, the description of X¹ described above is applied to X⁴ and X⁷, the description of X² described above is applied to X⁵ and X⁸, and the description of X³ described above is applied to X⁶ and X⁹, and the descriptions of R¹, R², and R³ in General Formula (I) described above can be respectively applied to R¹⁰¹, R¹⁰², and R¹⁰³ which are neither -L¹⁰-M nor -L¹¹-M.
• In >NR¹⁰¹ and >CR¹⁰²R¹⁰³ among X⁴ to X⁹, which have neither -L¹⁰-M nor -L¹¹-M, R¹⁰¹ is preferably an alkyl group, and R¹⁰² and R¹⁰³ are preferably a hydrogen atom.
• Regarding the two groups among X⁴ to X⁶, which do not have -L¹⁰-M described above, it is preferable that at least one thereof is >CR¹⁰²R¹⁰³, it is more preferable that at least one thereof is >CR¹⁰²R¹⁰³ and the remaining one is -O-, -S-, or >CR¹⁰²R¹⁰³, and it is still more preferable that both the two are >CR¹⁰²R¹⁰³.
• Regarding the two groups among X⁷ to X⁹, which do not have -L¹¹-M described above, it is preferable that at least one thereof is >CR¹⁰²R¹⁰³, it is more preferable that at least one thereof is >CR¹⁰²R¹⁰³ and the remaining one is -O-, -S-, or >CR¹⁰²R¹⁰³, and it is still more preferable that both the two are >CR¹⁰²R¹⁰³.
• Among X⁴ to X⁶, >NR¹⁰¹ or >CR¹⁰²R¹⁰³ which has -L¹⁰-M as any one of R¹⁰¹ to R¹⁰³ is preferably a group represented by >CR¹⁰²R¹⁰³ where R¹⁰³ is -L¹⁰-M, and it is more preferably a group represented by >CR¹⁰²R¹⁰³ where R¹⁰² is a hydrogen atom and R¹⁰³ is -L¹⁰-M.
• Among X⁷ to X⁹, >NR¹⁰¹ or >CR¹⁰²R¹⁰³ which has -L¹¹-M as any one of R¹⁰¹ to R¹⁰³ is preferably a group represented by >CR¹⁰²R¹⁰³ where R¹⁰³ is -L¹¹-M, and it is more preferably a group represented by >CR¹⁰²R¹⁰³ where R¹⁰² is a hydrogen atom and R¹⁰³ is -L¹¹-M.
• Among X⁴ to X⁶, the group having -L¹⁰-M is not particularly limited; however, it is preferably X⁵.
• Among X⁷ to X⁹, the group having -L¹¹-M is not particularly limited; however, it is preferably X⁸.
• L¹⁰ and L¹¹ are preferably a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, more preferably a group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, and still more preferably a group represented by * -L^x1-L^y1-**.
• To the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L¹⁰ and L¹¹, the description of the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L^a and L^b described above, can be applied unless otherwise specified.
• L^x1 is a single bond or a group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, and a heteroarylene group, and L^y1 is a single bond, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, or >P(=O)OR^B. It is noted that in *-L^x1-L^y1-**, * represents a bonding site to X⁴ to X⁹, and ** represents a bonding site to M.
• Among the groups represented by * -L^x1-L^y1-**, L¹⁰ and L¹¹ are preferably a group in which L^y1 is a single bond, -S-, >C=O, or >NR^A, more preferably a group in which L^y1 is >C=O or >NR^A, and still more preferably a group in which L^x1 is a single bond and L^y1 is >C=O or >NR^A.
• It is noted that in the compound represented by General Formula (V), it suffices that the number of shortest-distance atoms in the linking chain (each linking chain of the linking chain including L¹⁰ and the linking chain including L¹¹) that connects M to any one of X⁴ to X⁹ is, for example, 1 to 60, where 1 to 40 is preferable. In a case where M is a phosphor moiety, the above-described number of shortest-distance atoms means the number of atoms that constitute the shortest chain in the linking chain that connects a conjugated structural moiety for exhibiting fluorescence to any one of X⁴ to X⁹ in the phosphor moiety M.
• It is noted that in the compound represented by General Formula (V), it is also preferable that the structure represented by -(CH₂-CH₂-O)_b- described above (b is also as described above) is provided at any portion of the linking chain represented by "-linking group ZZZ-L¹⁰-" in the structure represented by "the conjugated structural moiety of M - the linking group ZZZ-L¹⁰- described above" and any portion of the linking chain represented by "-linking group ZZZ-L¹¹-" in the structure represented by "the conjugated structural moiety of M - the linking group ZZZ-L¹¹- described above".
<Compound represented by General Formula (VI)>
• The compound represented by General Formula (V) is preferably represented by General Formula (VI).

  
• In the formula, R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q. However, at least one of R^6A or R^7A represents Q.
• L¹² and L¹³ represent a linking group.
• na and nb are an integer of 0 or more.
• L¹⁰, L¹¹, X¹ to X⁹, M, Q, n, and m respectively have the same meanings as L¹⁰, L¹¹, X¹ to X⁹, M, Q, n, and m described above.
• However, any structure contained in ( )_n, ( )_na, or ( )_nb has at least any one of >NR¹ or >CR²R³, and each of the structures contained in ( )_n, ( )_na, and ( )_nb has a group including -(L-O)_gR^E, as at least one of R¹, R², or R³. R¹ to R³ which include the -(L-O)_gR^E are not bonded to at least any one of a phosphor or a biological substance. To the description of this definition, the description pertaining to the definitions (α) and (β) in General Formula (I) described above can be applied unless otherwise specified. That is, in the description pertaining to the structure parenthesized in ( )_n in the definitions (α) and (β) in General Formula (I) described above, in a case where the structure parenthesized in ( )_n is read as a structure parenthesized in ( )_na, and in addition, the structure parenthesized in ( )_n is as a structure parenthesized in ( )_nb, they can be respectively applied to the structure parenthesized in ( )_n, the structure parenthesized in ( )_na, and the structure parenthesized in ( )_nb, respectively.
• Unless otherwise specified, R^6A and R^7A have the same meanings as R^6A and R^7A in General Formula (IV) described above. That is, the description of R^6A and R^7A in General Formula (IV) can be applied to R^6A and R^7A.
• R^6A or R^7A and L¹² or L¹³ are each determined such that R^6A or R^7A is an unsubstituted group and L¹² or L¹³ is the longest group. However, in a case where the group represented by -L¹³R^6A or -L¹²R^7A has an anionic group, a cationic group, or Q, it is determined such that the anionic group, the cationic group, or Q, which is located on the most terminal side (the R^6A side in -L¹³R^6A or the R^7A side in -L¹²R^7A), is R^6A or R^7A.
• L¹² and L¹³ represent a linking group.
• The linking group which can be adopted as L¹² and L¹³ is, for example, an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, >C=O, >NR^A, >S=O, or it is preferably a linking group obtained by combining one or two or more of S(=O)₂ and >P (=O)OR^B. R^A and R^B represent a hydrogen atom or a substituent.
• To the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L¹² and L¹³, the description of the alkylene group, the alkenylene group, the alkynylene group, the arylene group, the heteroarylene group, >NR^A, and >P(=O)OR^B, which can constitute L⁷ or L⁸ in General Formula (IV) described above, can be applied.
• In the compound represented by General Formula (VI), it is preferable that (A) na is an integer of 1 or more and R^6A is Q, and/or (B) nb is an integer of 1 or more and R^7A is Q.
• However, the number of shortest linking atoms of L¹³ is 7 or less in a case of the (A), and the number of shortest linking atoms of L¹² is 7 or less in a case of the (B).
• Regarding the divalent linking group L¹³, "the number of shortest linking atoms in L¹³" means the number of atoms that constitute the shortest chain connecting N directly bonded to L¹³ to R^6A, in a case where na is an integer of 1 or more, where the N is one of those indicated in the structure parenthesized in ( )_na, and it means the number of atoms that constitute the shortest chain connecting N directly bonded to L¹³ to R^6A, in a case where na is 0, where the N is one of those indicated in the structure parenthesized in ( )_m.
• In addition, Regarding the divalent linking group L¹², "the number of shortest linking atoms in L¹²" means the number of atoms that constitute the shortest chain connecting >C=O directly bonded to L¹² to R^7A, in a case where nb is an integer of 1 or more, where the >C=O is one of those indicated in the structure parenthesized in ( )_nb, and it means the number of atoms that constitute the shortest chain connecting >C=O to R^7A, which is indicated on the left side of the structure parenthesized in ( )_nb in General Formula (VI), in a case where nb represents 0.
• For example, in a compound (6) that is used in Examples described later, since L¹² is -NHC₂H₄- and R^7A is -COOH, the number of shortest linking atoms of L¹² is 3.
• In the compound represented by General Formula (VI), at least one of R^6A or R^7A is Q. In particular, it is conceived that in a case of satisfying (A) and/or (B) described above, the mobility of the linker main chain is reduced, and thus the dye association can be further suppressed.
• The number of shortest linking atoms of L¹² and the number of shortest linking atoms of L¹³, which are described, are preferably 1 to 5 and more preferably 1 to 4.
• In the present invention, from the viewpoint of ease of synthesis, it is also preferable that any one of L¹² or L¹³ is a group including -(L-O)_g-.
• L¹² is more preferably a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, more preferably an -NR^A-alkylene group or an -NR^A-(L-O)_g-alkylene group, and still more preferably an -NR^A-alkylene group.
• L¹³ is more preferably a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and still more preferably >NR^A or >C=O.
• na and nb are an integer of 0 or more.
• In a case where R^6A is Q, na is preferably 0 to 20, more preferably 2 to 20, and still more preferably 4 to 18.
• In a case where R^7A is Q, nb is preferably 0 to 20, more preferably 2 to 20, and still more preferably 4 to 18.
• In a case where R^6A is not Q, na is preferably 0 to 20, more preferably 0 to 10, and still more preferably 0 to 5.
• In a case where R^7A is not Q, nb is preferably 0 to 20, more preferably 0 to 10, and still more preferably 0 to 5.
• In a case where a compound represented by any one of General Formulae (II) to (VI) among the compounds according to the embodiment of the present invention is obtained by using a peptide synthesis method, the structure is, in general, such that the C-terminal structure is on the right side of the paper surface, and the N-terminal structure is on the left side of the paper surface.
• The compound according to the embodiment of the present invention preferably contains at least one substituent represented by Q, that is, at least one of a carboxy group, a substituent capable of being bonded to a biological substance, or a substituent capable of being bonded to a solid support.
• The compound according to the embodiment of the present invention can be bonded to a biological substance by the carboxy group or a substituent capable of being bonded to a biological substance described later, whereby a targeted labeled biological substance can be obtained. It is noted that a substituent capable of being bonded to a biological substance can be easily derived from a carboxy group by a conventional method.
• In addition, the compound according to the embodiment of the present invention can be bonded to a solid support such as microparticles by the carboxy group or a substituent capable of being bonded to a solid support described later, whereby a targeted labeled microparticles can be obtained. The microparticle is not particularly limited; however, examples thereof include small particles that are useful for bonding to the compound according to the embodiment of the present invention, including a glass bead, a non-polymer bead such as a magnetic bead, and a polymer bead. In a certain embodiment, the microparticle includes a polystyrene bead. The small particle is not particularly limited as long as it has a size that is commonly used in the fluorescence labeling; however, the average particle diameter thereof is generally 10 nm to 10 µm. It is noted that a substituent capable of being bonded to a solid support can be easily derived from a carboxy group by a conventional method.
• In the present invention, for convenience, the substituent capable of being bonded to a biological substance and the substituent capable of being bonded to a solid support do not include a carboxy group, where "the substituent capable of being bonded to a biological substance" includes a substituent capable of being bonded to a biological substance, which is derived from a carboxy group, and "the substituent capable of being bonded to a solid support" includes a substituent capable of being bonded to a solid support, which is derived from a carboxy group. However, as described above, it is also possible to carry out bonding to a biological substance or a solid support by a carboxy group.
• In the compound according to the embodiment of the present invention, a position where the substituent represented by Q is provided is not particularly limited; however, the substituent represented by Q is preferably provided in a structure other than the structure represented by General Formula (I) and the phosphor moiety and more preferably provided in at least one of R⁶ or R⁷ in the compound represented by General Formula (II).
• It suffices that the number of substituents represented by Q in the compound according to the embodiment of the present invention is at least 1 or more in total, and it is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1, from the viewpoint of the quantification of the target substance to be detected.
• Specific examples of the compound according to the embodiment of the present invention will be shown below; however, the present invention is not limited to these compounds. In the following specific examples, Dye indicates a phosphor moiety.

  

  

  

  
• Examples of the preferred form according to the present invention include a compound satisfying the following form I among the compounds represented by General Formula (III) and a compound satisfying the following form II among the compounds represented by General Formula (V).
(Form I)
• Y¹ to Y³: A hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group
• Z¹ to Z³: An alkyl group, an aryl group, or a heteroaryl group
• W¹ to W³: A hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group
• LL¹ and LL²: >C=O, >NR^A, an alkylene group, an arylene group, or a heteroarylene group
• s, t, and u: An integer of 0 or 1
• R⁴ and R⁵: A hydrogen atom or an alkyl group
• R⁶: A substituent represented by -L⁷R^6A (L⁷ is a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and R^6A is an alkyl group, a sulfanyl group, an aryl group, a heteroaryl group, or Q.)
• R⁷: A substituent represented by -L⁸R^7A (L⁸ is a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and R^7A is an alkyl group, a sulfanyl group, an aryl group, a heteroaryl group, or Q.)
• L¹: >C=O, >NR^A, an arylene group, an alkylene group, -O-, or -S-
• L² and L⁵: A group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, and >NR^A
• L⁶: >C=O, >NR^A, or an arylene group
• X¹ to X³: At least two thereof are >CR²R³, and the remaining one is -O-, -S-, or >CR²R³. (R² and R³ are preferably a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E.)
• Phosphor moiety in M: A structural moiety consisting of at least one dye of a xanthene dye, a rhodamine dye, a coumarin dye, a cyanine dye, a pyrene dye, an oxazine dye, a squarylium dye, a pyridyloxazole dye, or a pyrromethene dye
• n: An integer of 2 to 72
• m: An integer of 1 to 30
(Form II)
• X⁴ to X⁶: A group in which a group having -L¹⁰-M is a group represented by >CR¹⁰²R¹⁰³ (R¹⁰² is a hydrogen atom, and R¹⁰³ is -L¹⁰-M), where at least one of two groups which do not have L¹⁰-M is >CR¹⁰²R¹⁰³ and the remaining one is -O-, -S-, or >CR¹⁰²R¹⁰³ (R¹⁰² and R¹⁰³ are preferably a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E.).
• X⁷ to X⁹: A group in which a group having -L¹¹-M is a group represented by >CR¹⁰²R¹⁰³ (R¹⁰² is a hydrogen atom, and R¹⁰³ is -L¹⁰-M), where at least one of two groups which do not have L¹¹-M is >CR¹⁰²R¹⁰³ and the remaining one is -O-, -S-, or >CR¹⁰²R¹⁰³ (R¹⁰² and R¹⁰³ are preferably a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E.).
• L¹⁰ and L¹¹: A single bond, or a group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, and >NR^A
• R⁶: A substituent represented by -L¹³R^6A (L¹³ is a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and R^6A is an alkyl group, a sulfanyl group, an aryl group, a heteroaryl group, or Q.)
• R⁷: A substituent represented by -L¹²R^7A (L¹² is a linking group obtained by combining one or two or more of an alkylene group, -O-, >C=O, and >NR^A, and R^7A is an alkyl group, a sulfanyl group, an aryl group, a heteroaryl group, or Q.)
• X¹ to X³: At least two thereof are >CR²R³, and the remaining one is -O-, -S-, or >CR²R³. (R² and R³ are preferably a hydrogen atom, -NR⁸R⁹, -OR¹⁰, or -(L-O)_gR^E.)
• Phosphor moiety in M: A structural moiety consisting of at least one dye of a xanthene dye, a rhodamine dye, a coumarin dye, a cyanine dye, a pyrene dye, an oxazine dye, a squarylium dye, a pyridyloxazole dye, or a pyrromethene dye
• n: An integer of 2 to 72
• m: An integer of 1 to 30
• In these forms, the above-described preferred descriptions pertaining to Y¹ to Y³, Z¹ to Z³, W¹ to W³, LL¹, LL², s, t, u, R⁴ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, n, and m can be applied to Y¹ to Y³, Z¹ to Z³, W¹ to W³, LL¹, LL², s, t, u, R⁴ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, n, and m in General Formula (III). In addition, to X⁴ to X⁹, L¹⁰, L¹¹, R⁶, R⁷, X¹ to X³, M, n, and m in General Formula (V), the above-described preferred descriptions pertaining to X⁴ to X⁹, L¹⁰, L¹¹, R⁶, R⁷, X¹ to X³, M, n, and m can be applied.
• The compound according to the embodiment of the present invention can be bonded to a biological substance such as a protein (including a peptide), an amino acid, a nucleic acid, a nucleotide, a sugar chain, or a lipid, by at least one substituent capable of being bonded to a biological substance, where the substituent is contained in the compound, and the compound can be used as a labeled biological substance.
• The substituent capable of being bonded to a biological substance can be used without particular limitation as long as it is a group for acting (including adhering) or bonding to a biological substance, and examples thereof include the substituents described in WO2002/026891A .
• Specific examples of "the substituent capable of being bonded to a biological substance" include the following structures.

  

  

  
• X means a halogen atom such as an iodine atom or a bromine atom. * represents a bonding site.
• In addition to the above, it is possible to use a peptide structure (a polyamino acid structure), a long-chain alkyl group, or the like can be used as the "substituent capable of being bonded to a biological substance".
• Among them, preferred examples thereof include an N-hydroxysuccinimide ester structure (an NHS ester structure), a succinimide structure, a maleimide structure, an azide group, an acetylene group, a peptide structure (a polyamino acid structure), a long-chain alkyl group (preferably having 12 to 30 carbon atoms), and a quaternary ammonium group.
• Among the compounds according to the embodiment of the present invention, specific examples of the compound having at least one substituent capable of being bonded to a biological substance also include, as a specific example, a form in which the carboxy group in the above-described exemplary compound according to the present invention is appropriately replaced with the substituent capable of being bonded to a biological substance described above. It is noted that the present invention is not limited to these compounds. For example, in the specific examples thereof, a group having a dissociative hydrogen atom such as a carboxy group or a sulfo group may adopt a salt structure by a hydrogen atom being dissociated therefrom.
• The compound according to the embodiment of the present invention can be bonded to a solid support such as the above-described microparticles by a substituent capable of being bonded to at least one solid support, the substituent being contained in the compound, and it can be used as a solid support reagent.
• The substituent that can be bonded to a solid support can be used without particular limitation as long as it is a group for acting on (including adhering to) or bonding to a solid support, and examples thereof preferably include the substituents described as the above-described substituent capable of being bonded to a biological substance. Among them, preferred examples thereof include an N-hydroxysuccinimide ester structure (an NHS ester structure), a succinimide structure, and a maleimide structure.
• Among the compounds according to the embodiment of the present invention, specific examples of the compound having at least one substituent capable of being bonded to a solid support also include, as a specific example, a form in which the carboxy group in the above-described exemplary compound of the compound according to the embodiment of the present invention is appropriately replaced with the substituent capable of being bonded to a solid support described above. It is noted that the present invention is not limited to these compounds. For example, in the specific examples thereof, a group having a dissociative hydrogen atom such as a carboxy group or a sulfo group may adopt a salt structure by a hydrogen atom being dissociated therefrom.
• The compound according to the embodiment of the present invention can be synthesized according to a conventional method. For example, it can be synthesized based on the peptide synthesis such as solid phase peptide synthesis, and a method that uses an automatic peptide synthesizer described in WO2018/174078A can also be preferably applied. The phosphor moiety, the physiologically active substance moiety, the prodrug moiety, and the radioactive isotope-containing moiety can also be synthesized based on a conventional method and introduced into the compound according to the embodiment of the present invention.
• A compound having a substituent capable of being bonded to a biological substance can also be synthesized according to a conventional method. For example, Bioconjugate Techniques (Third Edition, written by Greg T. Hermanson) can be referred to.
«Labeled biological substance»
• The labeled biological substance according to the embodiment of the present invention is a substance in which the compound according to the embodiment of the present invention, is bonded to a biological substance. Since the compound according to the embodiment of the present invention has fluorescence due to the phosphor moiety and exhibits an excellent fluorescence intensity, it can be preferably used for a labeled biological substance. The bond between the compound according to the embodiment of the present invention and a biological substance may have a form in which the compound according to the embodiment of the present invention and the biological substance are directly bonded or a form of being linked via a linking group.
• Preferred examples of the biological substance include a protein (including a peptide), an amino acid, a nucleic acid, a nucleotide, a sugar chain, and a lipid. Preferred examples of the protein include an antibody, and preferred examples of the lipid include a phospholipid, a fatty acid, and sterol, where a phospholipid is more preferable.
• Among the above biological substances, the clinically useful substance is not particularly limited; however, examples thereof include immunoglobulins such as immunoglobulin (Ig) G, IgM, IgE, IgA, and IgD; blood plasma proteins such as complement, C-reactive protein (CRP), ferritin, α₁ microglobulin, β₂ microglobulin, and antibodies thereof; tumor markers such as α-fetoprotein, carcinoembryonic antigen (CEA), prostate acid phosphatase (PAP), carbohydrate antigen (CA) 19-9, and CA-125, and antibodies thereof; hormones such as luteinizing hormone (LH), follicle-stimulating hormone (FSH), human ciliated gonadotropin (hCG), estrogen, and insulin, and antibodies thereof; and viral infection-related substances of viruses such HIV and ATL, hepatitis B virus (HBV)-related antigens (HBs, HBe, and HBc), human immunodeficiency virus (HIV), adult T-cell leukemia (ATL), and antibodies thereof.
• The examples thereof further include bacteria such as Corynebacterium diphtheriae, Clostridium botulinum, mycoplasma, and Treponema pallidum, and antibodies thereof; protozoa such as Toxoplasma, Trichomonas, Leishmania, Trypanosoma, and malaria parasites, and antibodies thereof; embryonic stem (ES) cells such as ELM3, HM1, KH2, v6.5, v17.2, v26.2 (derived from mice, 129, 129/SV, C57BL/6, and BALB/c), and antibodies thereof; antiepileptic drugs such as phenytoin and phenobarbital; cardiovascular drugs such as quinidine and digoxin; anti-asthma drugs such as theophylline; drugs such as antibiotics such as chloramphenicol and gentamicin, and antibodies thereof; and enzymes, extracellular toxins (for example, styrelidine O), and the like, and antibodies thereof. In addition, antibody fragments such as Fab'2, Fab, and Fv can also be used.
• The specific form in which the compound according to the embodiment of the present invention and a biological substance interact with each other to be bonded to each other includes, for example, the forms described below.
1. i) A non-covalent bond (for example, hydrogen bond, ionic bond including chelate formation) or a covalent bond between a peptide in the compound according to the embodiment of the present invention and a peptide in the biological substance,
2. ii) a Van der Waals force between a long-chain alkyl group in the compound according to the embodiment of the present invention and a lipid bilayer, a lipid, or the like in the biological substance,
3. iii) an amide bond formed by reacting an N-hydroxysuccinimide ester (NHS ester) in the compound according to the embodiment of the present invention with an amino group in the biological substance,
4. iv) a thioether bond formed by reacting a maleimide group in the compound according to the embodiment of the present invention with a sulfanyl group (-SH) in the biological substance, and
5. v) a formation of a triazole ring, which is formed by a Click reaction between an azide group in the compound according to the embodiment of the present invention and an acetylene group in the biological substance, or a Click reaction between an acetylene group in the compound according to the embodiment of the present invention and an azide group in the biological substance.
• However, in the form of the i) described above, the peptide in the compound of the present invention is not particularly limited as long as it is a peptide that is capable of forming a non-covalent bond or a covalent bond with a peptide in the biological substance, and preferred examples of the position where such a peptide is provided include R⁶ or R⁷ in General Formula (II).
• In addition to the forms i) to v) described above, the bonding can be formed, for example, in the form described in Lucas C. D. de Rezende and Flavio da Silva Emery. A Review of the Synthetic Strategies for the Development of BODIPY Dyes for Conjugation with Proteins, Orbital: The Electronic Journal of Chemistry, 2013, Vol 5, No. 1, p. 62-83. In addition, the method described in the same document can be appropriately referred to for the preparation of the labeled biological substance according to the embodiment of the present invention.
• Among the compounds according to the embodiment of the present invention, the labeled biological substance according to the embodiment of the present invention, which is obtained from a compound having a substituent capable of being bonded to a biological substance and a biological substance that is bonded to the compound by an interaction includes the compound in which a moiety other than the substituent capable of being bonded to a biological substance is replaced with the compound according to the embodiment of the present invention, and a product thereof, in the description of the compound example and the product in paragraph 0038 of JP2019-172826A . However, the present invention is not limited to these labeled biological substances and the like.
<Reagent containing labeled biological substance>
• In the reagent containing the labeled biological substance according to the embodiment of the present invention, the form of the labeled biological substance according to the embodiment of the present invention, for example, a solution form dissolved in an aqueous medium such as saline or a phosphate buffer solution, and a solid form such as a fine particle powder or a freeze-dried powder, is not particularly limited and can be appropriately selected depending on the purpose of use.
• For example, in a case where the labeled biological substance according to the embodiment of the present invention is used as a fluorescence labeling reagent, it can be used as a reagent containing the labeled biological substance having any one of the forms described above.
<Use application of labeled biological substance>
• The labeled biological substance according to the embodiment of the present invention, which is obtained from the compound according to the embodiment of the present invention, can exhibit an excellent fluorescence intensity and stably detect fluorescence emitted from the labeled biological substance excited by light irradiation. As a result, the labeled biological substance according to the embodiment of the present invention can be applied to various techniques using the fluorescence labeling, and it can be suitably used, for example, as a fluorescence labeling reagent in a multicolor WB or dot blotting or as a reagent for in vivo fluorescence imaging.
• The fluorescence detection carried out using the labeled biological substance according to the embodiment of the present invention usually includes the following processes (i) to (iii) or (iv) to (vii). The fluorescence detection including the processes (i) to (iii) corresponds to the direct method using a primary antibody fluorescently labeled with the compound according to the embodiment of the present invention, and the fluorescence detection including the processes (iv) to (vii) corresponds to the indirect method using a secondary antibody fluorescently labeled with the compound according to the embodiment of the present invention.
1. (i) The process of preparing each of the following (a) and (b)
   1. (a) A sample containing a targeted biological substance (hereinafter, also referred to as a "target biological substance")
   2. (b) A labeled biological substance according to the embodiment of the present invention (hereinafter, also referred to as a "labeled biological substance A according to the embodiment of the present invention") obtained by bonding the biological substance (hereinafter, also referred to as a "primary biological substance") capable of binding to the target biological substance in the above (a) to the compound according to the embodiment of the present invention
2. (ii) The process of preparing a conjugate (hereinafter, also referred to as a "fluorescently labeled conjugate A") in which the target biological substance in the above (a) is bonded to the primary biological substance in the labeled biological substance A according to the embodiment of the present invention in the above (b)
3. (iii) The process of irradiating the fluorescently labeled conjugate A with light having the range of the wavelength which is absorbed by the labeled biological substance A according to the embodiment of the present invention, and detecting the fluorescence emitted by the labeled biological substance A according to the embodiment of the present invention
4. (iv) The process of preparing each of the following (c) to (e)
   • (c) A sample containing a target biological substance
   • (d) A biological substance capable of binding to the target biological substance in the above (c) (hereinafter, also referred to as a "primary biological substance")
   • (e) A labeled biological substance according to the embodiment of the present invention (hereinafter, also referred to as a "labeled biological substance B according to the embodiment of the present invention") obtained by bonding the biological substance (hereinafter, also referred to as a "secondary biological substance") capable of binding to the primary biological substance in the above (d) to the compound according to the embodiment of the present invention (hereinafter, also referred to as a "labeled biological substance B according to the embodiment of the present invention")
5. (v) The process of preparing a conjugate (hereinafter, also referred to as a "conjugate b") in which the target biological substance in the above (c) is bonded to the primary biological substance of the above (d)
6. (vi) The process of preparing a conjugate (hereinafter, also referred to as a "fluorescently labeled conjugate B2") in which the primary biological substance in the conjugate b is bonded to the secondary biological substance in the labeled biological substance B according to the embodiment of the present invention
7. (vii) The process of irradiating the fluorescently labeled conjugate B2 with light having the range of the wavelength which is absorbed by the labeled biological substance B according to the embodiment of the present invention, and detecting the fluorescence emitted by the labeled biological substance B according to the embodiment of the present invention
• Examples of the biological substance (the primary biological substance) capable of binding to the target biological substance and the biological substance (the secondary biological substance) capable of binding to the primary biological substance include the biological substances in the labeled biological substance according to the embodiment of the present invention. The above biological substance can be appropriately selected in accordance with the target biological substance (a biological substance in the test object) or the primary biological substance, and a biological substance capable of specifically binding to the biological substance in the test object or to the primary biological substance can be selected.
• Examples of the protein among the target biological substances include a protein, which is a so-called disease marker. The disease marker is not particularly limited; however, examples thereof include α-fetoprotein (AFP), protein induced by vitamin K absence or antagonist II (PIVKA-II), breast carcinoma-associated antigen (BCA) 225, basic fetoprotein (BFP), carbohydrate antigen (CA) 15-3, CA19-9, CA72-4, CA125, CA130, CA602, CA54/61 (CA546), carcinoembryonic antigen (CEA), DUPAN-2, elastase 1, immunosuppressive acidic protein (IAP), NCC-ST-439, γ-seminoprotein (γ-Sm), prostate specific antigen (PSA), prostatic acid phosphatase (PAP), nerve specific enolase (NSE), Iba1, amyloid β, tau, flotillin, squamous cell carcinoma associated antigen (SCC antigen), sialyl LeX-i antigen (SLX), SPan-1, tissue polypeptide antigen (TPA), serial Tn antigen (STN), cytokeratin (CYFRA) pepsinogen (PG), C-reactive protein (CRP), serum amyloid A protein (SAA), myoglobin, creatine kinase (CK), troponin T, and ventricular muscle myosin light chain I.
• The target biological substance may be a bacterium. Examples of the bacterium include a bacterium to be subjected to a cellular and microbiological test, which is not particularly limited. Specific examples thereof include Escherichia coli, Salmonella, Legionella, and bacteria causing problems in public health.
• The target biological substance may be a virus. Although the virus is not particularly limited, examples of the virus antigen include hepatitis virus antigens such as hepatitis C and B virus antigens, p24 protein antigen of HIV virus, and pp65 protein antigen of cytomegalovirus (CMV), and E6 and E7 proteins of human papillomavirus (HPV).
• In the above (i) or (iv), the sample containing the target biological substance is not particularly limited and can be prepared according to a conventional method.
• In addition, the labeled biological substance according to the embodiment of the present invention is not particularly limited and can be prepared by bonding a biological substance capable of binding to a target biological substance to the compound according to the embodiment of the present invention, according to a conventional method. The form of the bond and the reaction to form the bond are as described above in the labeled biological substance according to the embodiment of the present invention.
• In the above (v), the target biological substance may be directly bonded to the primary biological substance or may be bonded through another biological substance which is different from the target biological substance and the primary biological substance. In addition, in the above (vi), the primary biological substance in the conjugate b may be directly bonded to the secondary biological substance in the labeled biological substance B according to the embodiment of the present invention or may be bonded through another biological substance which is different from the primary biological substance and the secondary biological substance.
• The labeled biological substance according to the embodiment of the present invention can be used as a fluorescently labeled antibody in both the direct method and the indirect method but is preferably used as a fluorescently labeled antibody in the indirect method.
• In the above (ii) or (v) and the above (vi), the binding of the labeled biological substance or the like according to the embodiment of the present invention to the target biological substance is not particularly limited and can be carried out according to a conventional method.
• In the above (iii) or (vii), the wavelength for exciting the labeled biological substance according to the embodiment of the present invention is not particularly limited as long as the wavelength is a luminescence wavelength (wavelength light) capable of exciting the labeled biological substance according to the embodiment of the present invention. Generally, the wavelength for excitation is preferably 300 to 1,000 nm and more preferably 400 to 800 nm.
• The fluorescence excitation light source used in the present invention is not particularly limited as long as it emits light having a luminescence wavelength (wavelength light) capable of exciting the labeled biological substance according to the embodiment of the present invention, and for example, various laser light sources can be used. In addition, various optical filters can be used to obtain a preferred excitation wavelength or detect only fluorescence.
• Other matters in the above (i) to (vii) are not particularly limited, and conditions of a method, a reagent, a device, and the like, which are generally used in the fluorescence detection using fluorescence labeling, can be appropriately selected.
• In addition, also regarding the processes other than the above (i) to (vii), conditions of a method, a reagent, a device, and the like, which are generally used, can be appropriately selected in accordance with various methods using fluorescence labeling.
• For example, in the multicolor WB using the labeled biological substance according to the embodiment of the present invention, it is possible to detect a target biological substance with excellent fluorescence intensity by preparing a blotted membrane according to a method generally used for a target biological substance (protein separation by electrophoresis, blotting to a membrane, and blocking of a membrane) and using the labeled biological substance according to the embodiment of the present invention as a labeled antibody (preferably, as a secondary antibody). In the dot blotting using the labeled biological substance according to the embodiment of the present invention, as in the case of the multicolor WB, it is possible to detect a target biological substance with excellent fluorescence intensity by preparing a blotted nitrocellulose membrane, a blotted PVDF (polyvinylidene fluoride) membrane, or the like according to a method generally used for a target biological substance and using the labeled biological substance according to the embodiment of the present invention as a labeled antibody (preferably, as a secondary antibody).
- Substituent group T -
• In the present invention, the preferred substituents include those selected from the following substituent group T.
• In addition, in the present invention, in a case of being simply described as a substituent, the substituent refers to this substituent group T, and in a case where an individual group, for example, an alkyl group is only described, a corresponding group in the substituent group T is preferably applied.
• Further, in the present invention, in a case where an alkyl group is described separately from a cyclic (cyclo)alkyl group, the alkyl group is meant to include a linear alkyl group and a branched alkyl group. On the other hand, in a case where an alkyl group is not described separately from a cyclic alkyl group, and unless otherwise specified, the alkyl group is meant to include a linear alkyl group, a branched alkyl group, and a cycloalkyl group. The same applies to groups (alkoxy group, alkylthio group, alkenyloxy group, and the like) containing a group capable of having a cyclic structure (alkyl group, alkenyl group, alkynyl group, and the like) and compounds containing a group capable of having a cyclic structure. In a case where a group is capable of forming a cyclic skeleton, the lower limit of the number of atoms of the group forming the cyclic skeleton is 3 or more and preferably 5 or more, regardless of the lower limit of the number of atoms specifically described below for the group that can adopt this structure.
• In the following description of the substituent group T, a group having a linear or branched structure and a group having a cyclic structure, such as an alkyl group and a cycloalkyl group, are sometimes described separately for clarity.
• The groups included in the substituent group T include the following groups.
• An alkyl group (preferably having 1 to 30 carbon atoms, more preferably having 1 to 20 carbon atoms, still more preferably having 1 to 12 carbon atoms, still more preferably having 1 to 8 carbon atoms, still more preferably having 1 to 6 carbon atoms, and particularly preferably having 1 to 3 carbon atoms), an alkenyl group (preferably having 2 to 30 carbon atoms, more preferably having 2 to 20 carbon atoms, still more preferably having 2 to 12 carbon atoms, still more preferably having 2 to 6 carbon atoms, and even still more preferably having 2 to 4 carbon atoms), an alkynyl group (preferably having 2 to 30 carbon atoms, still more preferably having 2 to 20 carbon atoms, still more preferably having 2 to 12 carbon atoms, still more preferably having 2 to 6 carbon atoms, and even still more preferably having 2 to 4 carbon atoms), a cycloalkyl group (preferably having 3 to 20 carbon atoms), a cycloalkenyl group (preferably having 5 to 20 carbon atoms), an aryl group (it may be a monocyclic group or may be a fused ring group (preferably a fused ring group of 2 to 6 rings); in a case of a fused ring group, the fused ring group consists of a 5- to 7-membered ring; and the aryl group preferably has 6 to 40 carbon atoms, more preferably has 6 to 30 carbon atoms, still more preferably has 6 to 26 carbon atoms, and particularly preferably has 6 to 10 carbon atoms), a heterocyclic group (it has, as a ring-constituting atom, at least one of a nitrogen atom, oxygen atom, a sulfur atom, a phosphorus atom, a silicon atom, or selenium atom, may be a monocyclic ring, or may be a fused ring group (preferably a fused ring group of 2 to 6 rings); in a case of a monocyclic group, the monocyclic ring is preferably a 5- to 7-membered ring and more preferably a 5-membered or 6-membered ring; the heterocyclic group preferably has 2 to 40 carbon atoms and more preferably having 2 to 20 carbon atoms; and the heterocyclic group includes an aromatic heterocyclic group (a heteroaryl group) and an aliphatic heterocyclic group), an alkoxy group (preferably having 1 to 20 carbon atoms, and more preferably having 1 to 12 carbon atoms), an alkenyloxy group (preferably having 2 to 20 carbon atoms, and more preferably having 2 to 12 carbon atoms), and an alkynyloxy group (preferably having 2 to 20 carbon atoms, and more preferably having 2 to 12 carbon atoms), a cycloalkyloxy group (preferably having 3 to 20 carbon atoms), an aryloxy group (preferably having 6 to 40 carbon atoms, more preferably having 6 to 26 carbon atoms, and still more preferably having 6 to 14 carbon atoms), a heterocyclic oxy group (preferably having 2 to 20 carbon atoms), a polyalkyleneoxy group,
• an alkoxycarbonyl group (preferably having 2 to 20 carbon atoms), a cycloalkoxycarbonyl group (preferably having 4 to 20 carbon atoms), an aryloxycarbonyl group (preferably having 6 to 20 carbon atoms), an amino group (preferably having 0 to 20 carbon atoms; the amino group includes an unsubstituted amino group (-NH₂), a (mono- or di-) alkylamino group, a (mono- or di-) alkenylamino group, a (mono- or di-) alkynylamino group, a (mono- or di-) cycloalkylamino group, a (mono- or di-) cycloalkenylamino group, a (mono- or di-) arylamino group, or a (mono- or di-) heterocyclic amino group, where each of the above groups substituting an unsubstituted amino group has the same definition as the corresponding group in the substituent group T), a sulfamoyl group (preferably having 0 to 20 carbon atoms; it is preferably an alkyl, cycloalkyl, or aryl sulfamoyl group), an acyl group (preferably having 1 to 20 carbon atoms, and more preferably having 2 to 15 carbon atoms; it includes -C(=O)H, an alkylcarbonyl group, a cycloalkylcarbonyl group, an arylcarbonyl group, and a heterocyclic carbonyl group), an acyloxy group (preferably having 1 to 20 carbon atoms), a carbamoyl group (preferably having 1 to 20 carbon atoms; it is preferably an alkyl, cycloalkyl, or aryl carbamoyl group),
• an acylamino group (preferably having 1 to 20 carbon atoms), a sulfonamide group (preferably having 0 to 20 carbon atoms and preferably an alkyl, cycloalkyl, or aryl sulfonamide group), an alkylthio group (preferably having 1 to 20 carbon atoms and more preferably having 1 to 12 carbon atoms), a cycloalkylthio group (preferably having 3 to 20 carbon atoms), an arylthio group (preferably having 6 to 40 carbon atoms, more preferably having 6 to 26 carbon atoms, and still more preferably having 6 to 14 carbon atoms), a heterocyclic thio group (preferably having 2 to 20 carbon atoms), an alkyl, cycloalkyl, or aryl sulfonyl group (preferably having 1 to 20 carbon atoms),
• a silyl group (preferably having 1 to 30 carbon atoms and more preferably having 1 to 20 carbon atoms; it is preferably a silyl group at which an alkyl, aryl, alkoxy, or aryloxy has been substituted), a silyloxy group (preferably having 1 to 20 carbon atoms: it is preferably a silyloxy group at which an alkyl, aryl, alkoxy, or aryloxy has been substituted), a hydroxy group, a cyano group, a nitro group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom or an iodine atom), an oxygen atom (specifically, >CH₂ which constitutes a ring is replaced with >C=O), a carboxy group (-CO₂H), a phosphono group [-PO(OH)₂], a phosphonooxy group [-O-PO(OH)₂], a sulfo group (-SO₃H), a borate group [-B(OH)₂], an onio group (also referred to as a cationic group; it includes an ammonio group including a cyclic ammonio group, a sulfonio group, and a phosphonio group, and it preferably has 0 to 30 carbon atoms and more preferably has 1 to 20 carbon atoms), a sulfanyl group (-SH), a guanidino group (-NHC(=NH)NH₂), an amino acid residue, and a polyamino acid residue.
(Anionic group)
• In the present invention, the anionic group may be any group having an anion. Examples of such an anionic group include a carboxy group, a phosphono group (a phosphonate group, -PO(OH)₂), a phosphonooxy group (a phosphate group, -OPO(OH)₂), and a sulfo group, where a phosphono group, a phosphonooxy group, or a sulfo group is preferable, and a phosphonooxy group or a sulfo group is more preferable.
• The anionic group may dissociate a hydrogen ion to have an ionic structure, or it may have a salt structure. To the monovalent or polyvalent cation in a case where the anionic group has a salt structure, the description of the monovalent or polyvalent cation in the description of the salt structure described above can be preferably applied.
(Cationic group)
• In the present invention, the cationic group may be any group having a cation. Examples of such a cationic group include a group having a quaternary ammonium ion and a group having a quaternary phosphonium ion, where a group having a quaternary ammonium ion is preferable. It is noted that preferred examples of the substituent possessed by N⁺ in the group having a quaternary ammonium ion and the substituent possessed by P⁺ in the group having a quaternary phosphonium ion include an alkyl group and an aryl group, where groups in which all the substituents possessed by N⁺ and P⁺ are alkyl groups are preferable.
• The cationic group may have a salt structure in addition to the ionic structure. Examples of the monovalent or polyvalent anion in a case where the cationic group has a salt structure include halide ions such as F^- and Cl^-, and monovalent or polyvalent organic anions such as BF₄ ^-, PF₆ ^-, and a bis(trifluoromethylsulfonyl)imide ion.
(Polyalkyleneoxy group)
• In the present invention, the polyalkyleneoxy group may be any group represented by -(L-O)_gR^E.
• The L represents an alkylene group obtained by removing one hydrogen atom from an alkyl group in the substituent group T described above, where it preferably has 2 to 4 carbon atoms, more preferably has 2 or 3 carbon atoms, and still more preferably has 2 carbon atoms. The number of carbon atoms contained in the shortest chain that links two carbon atoms which are bonding sites of the group is preferably 0 to 2, more preferably 0 or 1, and still more preferably 0. That is, L is most preferably an ethylene group.
• The g means an average repetition number (simply, also referred to as a repetition number) and is 1 to 24, and it is preferably 1 to 12 and more preferably 4 to 12. Even in a case where the repetition number is small, for example, even in a case where g is 1, the association of the phosphor moieties can be suppressed due to the steric repulsion between -(L-O)_gR^E in the structure represented by General Formula (I) and the phosphor moiety or the chain that links the phosphor moiety to a structure represented by General Formula (I), or the like, and an excellent fluorescence intensity can be exhibited.
• The R^E represents a hydrogen atom or an alkyl group. For the alkyl group which can be adopted as R^E, the description of the alkyl group in the above-described substituent group T can be preferably applied, and among the above, a methyl group is preferable. R^E is preferably a methyl group.
• In addition, examples of the group obtained by combining a plurality of substituents selected from the substituent group T include the above-described alkyl group, alkenyl group, alkynyl group, cycloalkyl group, cycloalkenyl group, aryl group, heterocyclic group, alkoxy group, alkenyloxy group, alkynyloxy group, cycloalkyloxy group, aryloxy group, heterocyclic oxy group, alkoxycarbonyl group, cycloalkoxycarbonyl group, aryloxycarbonyl group, amino group, sulfamoyl group, acyl group, acyloxy group, carbamoyl group, acylamino group, sulfonamide group, alkylthio group, cycloalkylthio group, arylthio group, heterocyclic thio group, and an alkyl, cycloalkyl, or aryl sulfonyl group, which have, as a substituent, an amino acid residue, a polyamino acid residue, or a polyalkyleneoxy group.
• The substituent selected from the substituent group T is more preferably an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a heterocyclic group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, a cycloalkoxycarbonyl group, an amino group, an acylamino group, a carbamoyl group, a cyano group, a halogen atom, an anionic group, a cationic group, or a polyalkyleneoxy group, and particularly preferably an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an alkoxy group, an acyl group, an alkoxycarbonyl group, an amino group, an acylamino group, a carbamoyl group, a cyano group, an anionic group, a cationic group, or a polyalkyleneoxy group.
• The substituent selected from the substituent group T also includes a group obtained by combining a plurality of the above groups, unless otherwise specified. For example, in a case where a compound, a substituent, or the like contains an alkyl group, an alkenyl group, or the like, the alkyl group, the alkenyl group, or the like may be substituted or unsubstituted. In addition, in a case where a compound, a substituent, or the like contains an aryl group, a heterocyclic group, or the like, the aryl group, the heterocyclic group, or the like may be a monocyclic ring or a fused ring moiety, and may be substituted or unsubstituted.
Examples
• Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited thereto. It is noted that room temperature means 25°C.
• Compounds (1) to (3) and (6) and comparative compounds (1) and (2), which are used in Examples and Comparative Examples, are shown below.
• It is noted that M¹ or M² in each compound indicates a phosphor moiety, which consists of a structure represented by each of the following structural formulae, and * represents a bonding site. In addition, in each compound, the sulfo group may include a salt structure (for example, a potassium salt, a sodium salt, a triethylammonium (TEA) salt, or an N,N-diisopropylethylammonium (DIPEA) salt), even unless otherwise specified.
• The compound (2) and the comparative compound (1) are compounds in which the distance between two M¹'s is about the same.
• In addition, the fluorescence intensity of the phosphor moieties M¹ and M² alone is about the same, and it is conceived that the difference in the phosphor moiety does not significantly contribute to the evaluation results of various fluorescence intensities pertaining to the labeled antibody described later.

  

  

  

  

  

  

  
• The method of synthesizing each compound and a labeled antibody will be described in detail below; however, the starting materials, the dye intermediates, and the synthetic routes are not limited thereto.
• It is noted that the abbreviations used in the synthesis of the respective compounds described below are as follows.
• DBU: 1,8-diazabicyclo[5.4.0]-7-undecene
• DIC: Diisopropylcarbodiimide
• PyAOP: (7-azabenzotriazole-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate
• DMT-MM: 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride
• EDCI: 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride
• HATU: 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate
• HOBt: 1-hydroxybenzotriazole
• NMP: N-methyl-2-pyrrolidone
• DMF: dimethylformamide
• DMAP: 4-dimethylaminopyridine
• DIPEA: N-diisopropylethylamine
• TEA: Triethylamine
• TFA: Trifluoroacetic acid
• TFE: 2,2,2-trifluoroethanol
• THF: Tetrahydrofuran
• Me: Methyl group
• Ms: Mesyl group
• Et: Ethyl group
• tBu: Tert-butyl group
• Ac: Acetyl group
• Ts: p-toluenesulfonyl group
• Trt: Trityl group (triphenylmethyl group)
• Fmoc: 9-fluorenylmethyloxycarbonyl group
• Boc: Tert-butoxycarbonyl group
• ivDde: A 1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3-methylbutyl group
• Ala: Alanine
• Gly: Glycine
• Lys: Lysine
• Pro: Proline
• Resin: Resin
• PEG_m: This indicates following structure, and m in PEG_m is the average repetition number. * represents a bonding site.
• EO_m: This indicates the following structure, and m in EO_m is the average repetition number. However, EO_m is bonded to a nitrogen atom or an oxygen atom on the carbon atom side. * represents a bonding site.
  
• In addition, %v/v means a percentage in terms of volume.
• Unless otherwise specified, SNAP Ultra C18 (product name, manufactured by Biotage, LLC) or Sfar C18 (product name, manufactured by Biotage, LLC) was used as the carrier in the reverse phase column chromatography, and Hi-Flash Column (product name, manufactured by Yamazen Corporation) was used as a carrier in the normal phase column chromatography.
• The mixing ratio in the eluent used in the reverse phase column chromatography or the normal phase column chromatography is in terms of the volume ratio. For example, "acetonitrile:water = from 0:100 to 20:80" means that the eluent of "acetonitrile:water = 0:100" was changed to an eluent of "acetonitrile:water = 20:80".
• For the preparative high performance liquid chromatography (HPLC), 2767 (product name, manufactured by Waters Corporation) was used.
• The MS spectrum was measured by ACQUITY SQD LC/MS System [product name, manufactured by Waters Corporation, ionization method: electrospray Ionization (ESI)] or LCMS-2010EV [product name, manufactured by Shimadzu Corporation, ionization method: an ionization method simultaneously carrying out ESI and atomospheric pressure chemical ionization (APCI)].
• It is noted that in the synthesis of each compound, the synthesis of the peptide chain was carried out according to the general method of the peptide solid phase method described in WO2018/174078A .
[General method of solid phase peptide synthesis method using automatic peptide synthesizer]
• Solid phase peptide synthesis was carried out using an automatic peptide synthesizer (product name: SyroI, manufactured by biotage, LLC). The synthesizer was set with Rink Amide-ChemMatrix (registered trade name, manufactured by Biotage, LLC), an N-methyl-2-pyrrolidone (NMP) solution of Fmoc amino acid (0.5 mol/L), an NMP solution of cyano-hydroxyimino-acetic acid ethyl ester (1.0 mol/L) and diisopropylethylamine (0.1 mol/L), an NMP solution of diisopropylcarbodiimide (1.0 mol/L), an NMP solution of piperidine (20% v/v), and an NMP solution of acetic anhydride (20 %v/v), and synthesis was carried out according to the manual. A procedure of Fmoc deprotection (20 minutes), washing with NMP, condensation of Fmoc amino acids (1 hour), and washing with NMP was set as one cycle, and this cycle was repeated to elongate the peptide chain.
[Synthesis of compound (M1-1)]
• A compound (M1-1) was synthesized based on the following scheme. It is noted that the compound (1-C) is the same as the compound (1-C) in the synthesis of a compound (M2-1) described later. The results of the MS measurement of the compound (5) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 1,723, (M - H⁺)^- = 1,721

  

  

  

  

  

  

  
<Synthesis of compound (1)> 1) Synthesis of compound (1-2)
• A compound (1-2) was synthesized according to the following scheme.

  
(i) Synthesis of compound (1-1)
• Solid phase peptide synthesis was carried out using H-Gly-Trt(2-Cl)-Resin (manufactured by Watanabe Chemical Industries, Ltd., 0.93 mmol/g, 53.8 mg) as a starting raw material. The elongation that was carried out by using N-[(9H-fluoren-9-ylmethoxy)carbonyl]glycine (Fmoc-Gly-OH) was repeated for 4 cycles. Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH) was subjected to elongation, and the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 12 cycles. Nε-(tert-butoxycarbonyl)-Nα-[(9H-fluoren-9-ylmethoxy)carbonyl)-L-lysine (Fmoc-Lys(Boc)-OH) was extended, Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH) was subjected to elongation, and then, an NMP solution of piperidine (20% v/v) was added thereto to carry out a reaction for 20 minutes, thereby carrying out the deprotection of the Fmoc group, and then, an NMP solution of acetic anhydride (20% v/v) was added thereto to carry out a reaction for 10 minutes, thereby subjecting the N-terminal amino group to acetylation. After completion of the elongation, the resin was washed with dichloromethane, and then the solvent was distilled off under reduced pressure. 2.0 mL of a mixed solution of TFA:triisopropylsilane:water = 95:2.5:2.5 was added thereto, and the peptide was cut out and deprotected. After 2 hours, the resin was filtered out, and methyl-t-butyl ether (12 mL) was added to the filtrate to generate a solid. The solid was precipitated by centrifugation, and then the supernatant was removed. The solid was washed with methyl-t-butyl ether, and then the solvent was distilled off under reduced pressure to obtain 55.2 mg of a white solid compound (1-1).
(ii) Synthesis of compound (1-2)
• 20.5 mg of the compound (1-1), 400 µL of N,N-dimethylformamide (DMF), 7.5 µL of triethylamine (Et₃N), and 8.8 mg of a methyl-PEG₄-NHS ester (a compound (α)) were placed in an eggplant flask having a capacity of 10 mL, and stirring was carried out at room temperature for 1 hour. Thereafter, 8.0 µL of hydrazine monohydrate was added thereto, and stirring was carried out at room temperature for 4 hours. The reaction solution was concentrated and purified by preparative HPLC, and freeze drying was followed to obtain 15.7 mg of a compound (1-2).
2) Synthesis of compound (1-NHS)
• A compound (1) was synthesized according to the following scheme, and further, a compound (1-NHS) was synthesized.

  
(i) Synthesis of compound (1)
• 1.5 mg of the compound (1-2), 150 µL of N,N-dimethylformamide (DMF), 1 µL of triethylamine (Et₃N), and 3.8 mg of the compound (M1-1) were placed in an eggplant flask having a capacity of 10 mL, and stirring was carried out at room temperature for 1 hour. Thereafter, the reaction solution was concentrated and purified by preparative HPLC, and freeze drying was followed to obtain 2.7 mg of a compound (1). The results of the MS measurement of the compound (1) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 5,520, (M - H⁺)^- = 5,518
(ii) Synthesis of compound (1-NHS)
• 270 µL of N,N-dimethylformamide (DMF), 1.2 mg of N,N,N',N'-tetramethyl-O-(N-succinimidyl)uronium hexafluorophosphate, and 1.3 µL of triethylamine (Et₃N) were added to 2.7 mg of the compound (1), and stirring was carried out for 1 hour. Then, the solvent was distilled off under reduced pressure, ethyl acetate was added, the supernatant was removed, and vacuum drying was carried out to obtain a compound (1-NHS).
<Synthesis of compound (2)> 1) Synthesis of compound (2-2)
• A compound (2-2) was synthesized according to the following scheme.

  
(i) Synthesis of compound (2-1)
• Solid phase peptide synthesis was carried out using H-Gly-Trt(2-Cl)-Resin (manufactured by Watanabe Chemical Industries, Ltd., 0.93 mmol/g, 53.8 mg) as a starting raw material. The elongation that was carried out by using N-[(9H-fluoren-9-ylmethoxy)carbonyl]glycine (Fmoc-Gly-OH) was repeated for 4 cycles. Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH) was subjected to elongation, and the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 2 cycles. (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was subjected to elongation, the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 3 cycles, (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was subjected to elongation, and the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 3 cycles. (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was subjected to elongation, and N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was subjected to elongation. Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH) was subjected to elongation, and then, an NMP solution of piperidine (20% v/v) was added thereto to carry out a reaction for 20 minutes, thereby carrying out the deprotection of the Fmoc group, and then, an NMP solution of acetic anhydride (20% v/v) was added thereto to carry out a reaction for 10 minutes, thereby subjecting the N-terminal amino group to acetylation. After completion of the elongation, the resin was washed with dichloromethane, and then the solvent was distilled off under reduced pressure. 2.0 mL of a mixed solution of TFA:triisopropylsilane:water = 95:2.5:2.5 was added thereto, and the peptide was cut out and deprotected. After 2 hours, the resin was filtered out, and methyl-t-butyl ether (12 mL) was added to the filtrate to generate a solid. The solid was precipitated by centrifugation, and then the supernatant was removed. The solid was washed with methyl-t-butyl ether, and then the solvent was distilled off under reduced pressure to obtain 63.5 mg of a white solid compound (2-1).
(ii) Synthesis of compound (2-2)
• 3.8 mg of a compound (2-2) was synthesized from 5.0 mg of the compound (2-1) in the same manner as in the synthesis of the compound (1-2).
2) Synthesis of compound (2)
• 3.0 mg of the above-described compound (2) was synthesized from 2.0 mg of the compound (2-2) in the same manner, except that in the synthesis of the compound (1) described above, the compound (2-2) was used instead of the compound (1-2). The results of the MS measurement of the compound (2) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 5,873, (M - H⁺)^- = 5,871
3) Synthesis of compound (2-NHS)
• The following compound (2-NHS) was synthesized in the same manner, except that in the synthesis of the compound (1-NHS) described above, the compound (2) was used instead of the compound (1).

  
<Synthesis of compound (3)>
• A compound (3-9) was synthesized according to the following scheme.

  
(i) Synthesis of compound (3-1)
• Solid phase peptide synthesis was carried out using H-Pro-Trt(2-Cl)-Resin (manufactured by Watanabe Chemical Industries, Ltd., 0.94 mmol/g, 638.4 mg) as a starting raw material. N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was subjected to elongation. (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was subjected to elongation, the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 3 cycles, (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was subjected to elongation, and the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 3 cycles. (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) and N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) were subjected to elongation in this order, and then, Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH) was subjected to elongation.
• After completion of the elongation, the resin was washed with dichloromethane, and then the solvent was distilled off under reduced pressure. 2.0 mL of a mixed solution of TFA:triisopropylsilane:water = 95:2.5:2.5 was added thereto, and the peptide was cut out and deprotected. After 2 hours, the resin was filtered out, and methyl-t-butyl ether (12 mL) was added to the filtrate to generate a solid. The solid was precipitated by centrifugation, and then the supernatant was removed. The solid was washed with methyl-t-butyl ether, and then the solvent was distilled off under reduced pressure to obtain 657.2 mg of a white solid compound (3-1).
(ii) Synthesis of compound (3-2)
• 657.2 mg of the compound (3-1), 13 mL of N,N-dimethylformamide (DMF), 513 µL of triethylamine (Et₃N), and 614 mg of a methyl-PEG₄-NHS ester were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 1 hour. The reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 758.9 mg of a compound (3-2).
(iii) Synthesis of compound (3-4)
• 300 mg of the compound (4-1) described in WO2020/175473A as the compound (3-3), 3 mL of tetrahydrofuran (THF), 230.6 mg of Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH), 76.8 µL of diisopropylcarbodiimide, and 8.0 mg of 4-dimethylaminopyridine were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 2 hours. Acetonitrile (30 mL) was added thereto to filter the precipitated solid, which was subsequently subjected to drying under reduced pressure to obtain 345 mg of a compound (3-4).
(iv) Synthesis of compound (3-5)
• 105 mg of the compound (3-4), 1 mL of chloroform (CHCl₃), and 21.5 µL of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at 35°C for 1 hour. 9.5 µL of methanesulfonic acid (MsOH), 50.2 µL of N,N-diisopropylethylamine (DIPEA), 211 mg of the compound (3-2), and 49.6 mg of (7-azabenzotriazole-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyAOP) were placed therein, and stirring was carried out at 35°C for 3 hours. A solid precipitated by adding acetonitrile (10 mL) was subjected to filtration and drying under reduced pressure to obtain an intermediate compound.
• The same operation was repeated twice to obtain 261.9 mg of a compound (3-5).
(v) Synthesis of compound (3-6)
• 200 mg of the compound (3-5), 5 mL of chloroform (CHCl₃), and 8.3 µL of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) were placed in an eggplant flask having a capacity of 100 mL, and stirring was carried out at 35°C for 1 hour. 7.6 µL of methanesulfonic acid (MsOH), 15.4 µL of N,N-diisopropylethylamine (DIPEA), and 5.9 µL of acetic anhydride (Ac₂O) were placed therein, and stirring was carried out at 35°C for 1 hour. Acetonitrile (50 mL) was added thereto to filter the precipitated solid, which was subsequently subjected to drying under reduced pressure to obtain 157 mg of a compound (3-6).
(vi) Synthesis of compound (3-7)
• 30.0 mg of the compound (3-6), 600 µL of chloroform (CHCl₃), 60 µL of 2,2,2-trifluoroethanol (TFE), and 6 µL of trifluoroacetic acid (TFA) were placed in an eggplant flask having a capacity of 10 mL, and stirring was carried out at room temperature for 4 hours. Thereafter, the reaction solution was filtered, and 6 mL of methanol (MeOH) was added to the filtrate to generate a precipitate, which was subsequently centrifuged. The recovered compound was purified by preparative HPLC and subjected to freeze drying to obtain 18.2 mg of a compound (3-7).
(vii) Synthesis of compound (3-8)
• 15 mg of the compound (3-7), 200 µL of water, 200 µL of N,N-dimethylformamide (DMF),1.5 mg of tert-butyl 1-amino-3,6,9,12-tetraoxadecane-15-ate, and 2.4 mg of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) were placed in an eggplant flask having a capacity of 10 mL, and stirring was carried out at room temperature for 2 hours. Then, the reaction solution was concentrated, 400 µL of trifluoroacetic acid (TFA) was added thereto, and stirring was carried out at room temperature for 30 minutes. Thereafter, the reaction solution was concentrated and purified by preparative HPLC, and freeze drying was followed to obtain 13.9 mg of a compound (3-8).
(viii) Synthesis of compound (3-9)
• 10 mg of the compound (3-8), 200 µL of N,N-dimethylformamide (DMF), and 4.0 µL of hydrazine monohydrate were placed in an eggplant flask having a capacity of 10 mL, and stirring was carried out at room temperature for 4 hours. Thereafter, the reaction solution was concentrated and purified by preparative HPLC, and freeze drying was followed to obtain 5.6 mg of a compound (3-9).
2) Synthesis of compound (3)
• 3.5 mg of the above-described compound (3) was synthesized from 2.0 mg of the compound (3-9) in the same manner, except that in the synthesis of the compound (1) described above, the compound (3-9) was used instead of the compound (1-2). The results of the MS measurement of the compound (3) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 13,227, (M - H⁺)^- = 13,225
3) Synthesis of compound (3-NHS)
• The following compound (3-NHS) was synthesized in the same manner, except that in the synthesis of the compound (1-NHS) described above, the compound (3) was used instead of the compound (1).

  
<Synthesis of comparative example compound (1)> 1) Synthesis of compound (4-7)
• A compound 4-7) was synthesized according to the following scheme.

  
(i) Synthesis of compound (4-3)
• 750 mg of Nε-(1-(4,4-dimethyl-2,6-dioxocyclohexa-1-ylidene)-3-methylbutyl)-Nα-[(9H-fluoren-9-ylmet hoxy)carbonyl)-L-lysine (Fmoc-Lys(ivDde)-OH) as the compound (4-1), 15 mL of tetrahydrofuran (THF), 461 mg of tert-butyl 1-amino-3,6,9,12-tetraoxadecane-15-ate, 595 mg of 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), and 273 µL of N,N-diisopropylethylamine (DIPEA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 4 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, and then the organic layer was distilled off under reduced pressure to obtain a compound (4-2) as a crude product.
• The compound (4-2), 7.5 mL of tetrahydrofuran (THF), and 258 µL of piperidine were placed in an eggplant flask having a capacity of 50 mL and stirred at room temperature for 12 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, the organic layer was distilled off under reduced pressure, and the purification was carried out by normal phase column chromatography to obtain 855 mg of a compound (4-3).
(ii) Synthesis of compound (4-4)
• 300 mg of the compound (4-3), 7.7 mL of dichloromethane (CH₂Cl₂), 83.2 µL of acetic anhydride (Ac₂O), and 139 µL of triethylamine (TEA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 1 hour. Thereafter, liquid separation was carried out with chloroform (CHCL₃) and saturated saline, and then the organic layer was distilled off under reduced pressure to obtain a crude product.
• The obtained crude product and 3.5 mL of trifluoroacetic acid (TFA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 30 minutes. Thereafter, the reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 287 mg of a compound (4-4).
(iii) Synthesis of compound (4-5)
• 287 mg of the compound (4-4), 5.7 mL of tetrahydrofuran (THF), 172 mg of tert-butyl 1-amino-3,6,9,12-tetraoxadecane-15-ate, 255 mg of 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), and 117 µL of N,N-diisopropylethylamine (DIPEA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 4 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, and then the organic layer was distilled off under reduced pressure to obtain a compound as a crude product.
• The obtained crude product and 2.5 mL of trifluoroacetic acid (TFA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 30 minutes. Thereafter, the reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 281 mg of a compound (4-5).
(iv) Synthesis of compound (4-6)
• 140 mg of the compound (4-5), 2.8 mL of tetrahydrofuran (THF), 103 mg of the compound (4-3), 71.9 mg of 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), and 33.0 µL of N,N-diisopropylethylamine (DIPEA), were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 4 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, and then the organic layer was distilled off under reduced pressure to obtain a compound as a crude product.
• The obtained crude product, 2.8 mL of tetrahydrofuran (THF), and 30.6 µL of hydrazine monohydrate were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 12 hours. Thereafter, the reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 152 mg of a compound (4-6).
(v) Synthesis of compound (4-7)
• 108 mg of the compound (4-6) and 3 mL of trifluoroacetic acid (TFA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 1.5 hours. Thereafter, the reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 100 mg of a compound (4-7).
2) Synthesis of comparative compound (1)
• 3.9 mg of the above-described comparative compound (1) was synthesized from 2.2 mg of the compound (4-7) in the same manner, except that in the synthesis of the compound (1) described above, the compound (4-7) was used instead of the compound (1-2). The results of the MS measurement of the comparative compound (1) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 4,466, (M - H⁺)^- = 4,464
3) Synthesis of comparative compound (1-NHS)
• The following comparative compound (1-NHS) was synthesized in the same manner, except that in the synthesis of the compound (1-NHS) described above, the comparative compound (1) was used instead of the compound (1).

  
<Synthesis of comparative compound (2)> 1) Synthesis of compound (5-4)
• A compound (5-4) was synthesized according to the following scheme.

  
(i) Synthesis of compound (5-1)
• 300 mg of the compound (4-3), 15 mL tetrahydrofuran (THF), 250 mg of 15-[(tert-butoxycarbonyl)amino]-4,7,10,13-tetraoxapentadecanoic acid, 348 mg of 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), and 132 µL of N,N-diisopropylethylamine (DIPEA) were placed in an eggplant flask having a capacity of 100 mL, and stirring was carried out at room temperature for 4 hours. Subsequently, 5 mL of trifluoroacetic acid (TFA) was placed therein, and stirring was carried out at room temperature for 3 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, the organic layer was distilled off under reduced pressure, and the purification was carried out by reverse phase column chromatography to obtain 352 mg of a compound (5-1).
(ii) Synthesis of compound (5-2)
• 300 mg of the compound (4-4), 15 mL tetrahydrofuran (THF), 173 mg of Nε-(tert-butoxycarbonyl)-L-lysine (H-Lys(Boc)-OH), 355 mg of 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), and 134 µL of N,N-diisopropylethylamine (DIPEA) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 4 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, the organic layer was distilled off under reduced pressure, and the purification was carried out by reverse phase column chromatography to obtain 348 mg of a compound (5-2).
(iii) Synthesis of compound (5-3)
• 150 mg of the compound (5-2), 3.0 mL of tetrahydrofuran (THF), 217 mg of the compound (5-1), 126 mg of 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), and 47.8 µL of N,N-diisopropylethylamine (DIPEA), were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 4 hours. Subsequently, 1.5 mL of trifluoroacetic acid (TFA) was placed therein, and stirring was carried out at room temperature for 3 hours. Thereafter, liquid separation was carried out with ethyl acetate and saturated saline, the organic layer was distilled off under reduced pressure, and the purification was carried out by reverse phase column chromatography to obtain 198 mg of a compound (5-3).
(iv) Synthesis of compound (5-4)
• 32.8 mg of a compound (5-4) was synthesized from 50.0 mg of the compound (5-3) in the same manner as in the synthesis of the compound (2-2).
2) Synthesis of comparative compound (2)
• 3.2 mg of the above-described comparative compound (2) was synthesized from 2.1 mg of the compound (5-4) in the same manner, except that in the synthesis of the compound (1) described above, the compound (5-4) was used instead of the compound (1-2). The results of the MS measurement of the comparative compound (2) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 4,812, (M - H⁺)^- = 4,810
3) Synthesis of comparative compound (2-NHS)
• The following comparative compound (2-NHS) was synthesized in the same manner, except that in the synthesis of the compound (1-NHS) described above, the comparative compound (2) was used instead of the compound (1).

  
[Synthesis of compound (M2-1)]
• A compound (M2-1) was synthesized based on the following scheme. The results of the MS measurement of the compound (7) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 1,384, (M - H⁺)^- = 1,382

  
<Synthesis of compound (6)> 1) Synthesis of compound (6-11)
• A compound (6-11) was synthesized according to the following scheme.

  
(i) Synthesis of compound (6-1)
• Solid phase peptide synthesis was carried out using H-Pro-Trt(2-Cl)-Resin (manufactured by Watanabe Chemical Industries, Ltd., 0.93 mmol/g, 53.8 mg) as a starting raw material. N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) and (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) were subjected to elongation, and the elongation that was carried out by using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 3 cycles. (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH (2S,4S)) was subjected to elongation, and the elongation using N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) was repeated for 3 cycles. (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) and N-(9-fluorenylmethoxycarbonyl)-L-proline (Fmoc-Pro-OH) were subjected to elongation. After completion of the elongation, the resin was washed with dichloromethane, and then the solvent was distilled off under reduced pressure. 2.0 mL of a mixed solution of TFA:triisopropylsilane:water = 95:2.5:2.5 was added thereto, and the peptide was cut out and deprotected. After 2 hours, the resin was filtered out, and methyl-t-butyl ether (12 mL) was added to the filtrate to generate a solid. The solid was precipitated by centrifugation, and then the supernatant was removed. The solid was washed with methyl-t-butyl ether, and then the solvent was distilled off under reduced pressure to obtain 51.2 mg of a white solid compound (6-1).
(ii) Synthesis of compound (6-2)
• 352 mg of the compound (6-1), 3.5 mL of chloroform (CHCl₃), 423 µL of N-diisopropylethylamine (DIPEA), and 115 µL of acetic anhydride (Ac₂O) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 1 hour. Thereafter, the reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 314 mg of a compound (6-2).
(iii) Synthesis of compound (6-3)
• 372 mg of the compound (6-1), 5.5 mL of chloroform (CHCl₃), 403 µL of N-diisopropylethylamine (DIPEA), and 346 mg of methyl-PEG₄-NHS ester were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at room temperature for 1 hour. The reaction solution was concentrated and purified by reverse phase column chromatography, and freeze drying was followed to obtain 499 mg of a compound (6-3).
(iv) Synthesis of compound (6-4)
• 593 mg of the above-described compound (6-4) was synthesized from 500 mg of the compound (2-1) in the same manner, except that in the synthesis of the compound (3-4) described above, N-[(9H-fluoren-9-ylmethoxy)carbonyl]-β-alanine (Fmoc-βAla-OH) was used instead of Nα-(9H-fluoren-9-ylmethoxy)carbonyl)-Nε-[1-(4,4-dimethyl-2,6-dioxocyclohexy-1-ylidene)-3 -methylbutyl]-L-lysine (Fmoc-Lys(ivDde)-OH).
(v) Synthesis of compound (6-5)
• 108 mg of the compound (6-4), 2.2 mL of chloroform (CHCl₃), and 26.8 µL of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) were placed in an eggplant flask having a capacity of 50 mL, and stirring was carried out at 35°C for 1 hour. 11.7 µL of methanesulfonic acid (MsOH), 93.3 µL of N,N-diisopropylethylamine (DIPEA), 169 mg of the compound (6-2), and 141 mg of (7-azabenzotriazole-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyAOP) were placed therein, and stirring was carried out at 35°C for 3 hours. A solid precipitated by adding acetonitrile (10 mL) was subjected to filtration and drying under reduced pressure to obtain 219 mg of a compound (6-5).
(vi) Synthesis of compound (6-6)
• 233 mg of the above-described compound (6-6) was synthesized from 219 mg of the compound (6-5) in the same manner, except that in the synthesis of the compound (6-5) described above, (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was used instead of the compound (6-2).
(vii) Synthesis of compound (6-7)
• 69.5 mg of the above-described compound (6-7) was synthesized from 38.0 mg of the compound (6-6) in the same manner, except that in the synthesis of the compound (6-5) described above, the compound (6-3) was used instead of the compound (6-2).
(viii) Synthesis of compound (6-8)
• 48.9 mg of the above-described compound (6-8) was synthesized from 69.5 mg of the compound (6-7) in the same manner, except that in the synthesis of the compound (6-5) described above, (2S,4S)-(tert-butoxycarbonyl)-4-amino-1-(9H-fluoren-9-ylmethoxy)carbonyl)-pyrrolidine-2-ca rboxylic acid (Fmoc-L-Pro(4-NHBoc)-OH(2S,4S)) was used instead of the compound (6-2).
(ix) Synthesis of compound (6-9)
• The same operation as the above-described synthesis of the compounds (6-7) and (6-8) was repeated twice to synthesize 60.5 mg of a compound (6-9) from 48.9 mg of the compound (6-8).
(x) Synthesis of compound (6-10)
• 40.1 mg of the above-described compound (6-10) was synthesized from 60.5 mg of the compound (6-9) in the same manner, except that in the synthesis of the compound (3-6) described above, the compound (6-9) was used instead of the compound (3-5).
(xi) Synthesis of compound (6-11)
• 40.1 mg of the compound (6-10) and 1.0 mL of a mixed solution of TFA:triisopropylsilane:water = 95:2.5:2.5 were added to an eggplant flask having a capacity of 10 mL, and stirring was carried out at room temperature for 1 hour. 10 mL of the reaction solution of methanol (MeOH) was added thereto to generate a solid to be removed, and then the solid was removed by filtration. The filtrate was concentrated and purified by preparative HPLC, and freeze drying was followed to obtain 16.8 mg of a compound (6-11).
Synthesis of compound (6)
• 0. 75 mg of the above-described compound (6) was synthesized from 2.0 mg of the compound (6-11n the same manner, except that in the synthesis of the compound (1) described above, the compound (6-11 was used instead of the compound (1-2) and the compound (M2-1) was used instead of the compound (M1-1). The results of the MS measurement of the compound (6) were as follows.
  MS (ESI m/z): (M + H⁺)⁺ = 9,633, (M - H⁺)^- = 9,631
Synthesis of compound (6-NHS)
• The following compound (6-NHS) was synthesized in the same manner, except that in the synthesis of the compound (1-NHS) described above, the compound (6) was used instead of the compound (1).

  
<Example 1>
• For each of the above-described compounds, the solution fluorescence intensity, the dot blot fluorescence intensity, and the Western blotting fluorescence intensity were evaluated as an indicator of suitability in a usage form of an application to a solution and an application to a membrane in a case of being used as a labeling substance.
[0] Preparation of fluorescently labeled antibody
• 104 µL of an anti-rabbit IgG antibody (2.3 mg/ml) and 10.4 µL of a carbonate buffer were added to a microtube, the resultant mixture was shaken and stirred. Then, a dimethyl sulfoxide solution of the compound (1-NHS) was added thereto so that the molar equivalent ratio of the compound (1-NHS) with respect to 1 equivalent of the antibody was as shown in Table A, and further, the resultant mixture was shaken and stirred. After being allowed to stand at 4°C for 24 hours, the reaction solution was subjected to purification, by using a centrifugal ultrafiltration filter (product name: Amicon Ultra UFC 510096, manufactured by Merck KGaA) and a PBS solution (phosphate-buffered saline), to obtain an IgG antibody labeled with the compound (1). Similarly, antibodies labeled with the respective compounds and comparative compounds were obtained. The degree of fluorescence labeling (DOL) of the obtained labeled antibody was calculated according to the method described below. The results are summarized in Table A.
• As the method for calculating the degree of fluorescence labeling, such a general method as described below was used. The description in [ ] indicates a unit, and [-] means that there is no unit. In the present test, protein means an anti-rabbit IgG antibody. $$\mathrm{Degree}\mathrm{of}\mathrm{fluorescence}\mathrm{labeling}=\mathrm{fluorescent}\mathrm{dye}\mathrm{concentration}/\mathrm{protein}\mathrm{concentration}$$

  
• The fluorescent dye concentration means the total molar concentration [M] of the labeled fluorescent dye, and the protein concentration means the molar concentration [M] of the fluorescently labeled protein. They are respectively calculated according to the following expressions.
• Fluorescent dye concentration = Dye_max/ε_dye
• Protein concentration = (IgG₂₈₀ - (Dye_max × CF))/ε_protein
• Each symbol in the above expressions is as follows.
• Dye_max: Absorption [-] of fluorescent dye at maximum absorption wavelength
• ε_dye: Molar absorption coefficient [M^-1cm^-1] of fluorescent dye
• IgG₂₈₀: Absorption [-] of fluorescently labeled protein at 280 nm
• Dye₂₈₀: Absorption [-] of fluorescent dye at 280 nm
• ε_protein: Molar absorption coefficient [M^-1cm^-1] of protein
• Correction Factor (CF): Dye₂₈₀/Dye_max [-]
[Table A]

No.	Labeled antibody	10 equivalents	15 equivalents	20 equivalents	30 equivalents
001	Compound (1) - IgG	3.1	4.1	5.9	-
002	Compound (2) - IgG	3.3	4.2	5.8	-
003	Compound (3) - IgG	3.2	4.1	6.0	-
004	Compound (6) - IgG	3.1	-	-	4.3
c01	Comparative compound (1) - IgG	3.0	4.6	5.7	-
c02	Comparative compound (2) - IgG	3.1	4.0	5.9	-

(Note in table)

• In the column of the labeled antibody, the notation of Compound (Z) - IgG or Comparative compound (Z) - IgG means an IgG antibody labeled with the compound (Z-NHS) or an IgG antibody labeled with the comparative compound (Z-NHS). Here, Z means the number of each compound. The same applies to the following tables.
• From the results in Table A above, the following facts can be seen.
• Even in a case where the compounds (1) to (3), which are the compounds according to the embodiment of the present invention, are added at any molar equivalent ratio of 10 equivalents, 15 equivalents, or 20 equivalents, with respect to 1 equivalent of the antibody, they exhibit the degree of fluorescence labeling equal to or higher than that in a case where the comparative compound (1) or (2) which does not have a structure represented by General Formula (I) is used, and the binding property to the antibody is at a sufficient level without any problem in practical use. This fact can be read from the comparison between No. c01 or c02 and Nos. 001 to 003. In addition, even in a case where the compound (6), which is the compound according to the embodiment of the present invention, is added at any molar equivalent ratio of 10 equivalents or 30 equivalents, with respect to 1 equivalent of the antibody, the degree of fluorescence labeling is 3.1 or more, and the binding property to the antibody is at a sufficient level without any problem in practical use.
• It is noted that in the following evaluation of the fluorescence intensity, it is possible to compare the fluorescence intensities in a state where the numbers of phosphor moieties bonded to proteins are arranged to be about the same by comparing examples in which the product of the number of phosphor moieties in the compound and the degree of fluorescence labeling (DOL) is about the same.
[1] Evaluation of solution fluorescence intensity
• A solution of the labeled antibody prepared as described above was prepared to have a protein concentration of 0.005 mg/mL, and the integrated value of the fluorescence intensity in a fluorescence wavelength range of 810 to 840 nm was calculated by using a spectroscopic fluorescence intensity meter (product name: RF-5300, manufactured by Shimadzu Corporation) with excitation light of 785 nm and unified the exposure conditions. Using the integrated value of the fluorescence intensity of the comparative compound (1) - IgG having DOL of 3.0 (addition of 10 equivalents of dye) in a fluorescence wavelength range of 810 to 840 nm as the reference value, the ratio to this reference value (the integrated value of the fluorescence intensity of the labeled antibody in a fluorescence wavelength range of 810 to 840 nm/the reference value) was calculated, and evaluation was carried out based on the following evaluation standards. The results are summarized in Table 1.
- Evaluation standards for fluorescence intensity (integrated value) -
• AAA: The ratio of fluorescence intensity to the reference value is 2.4 times or more.
• AA: The ratio of fluorescence intensity to the reference value is 2.2 times or more and less than 2.4 times.
• A: The ratio of fluorescence intensity to the reference value is 2.0 times or more and less than 2.2 times.
• B: The ratio of fluorescence intensity to the reference value is 1.8 times or more and less than 2.0 times.
• C: The ratio of fluorescence intensity to the reference value is 1.5 times or more and less than 1.8 times.
• D: The ratio of fluorescence intensity to the reference value is 1.3 times or more and less than 1.5 times.
• E: The ratio of fluorescence intensity to the reference value is 1.1 times or more and less than 1.3 times.
• F: The ratio of fluorescence intensity to the reference value is 0.8 times or more and less than 1.1 times.
• G: The ratio of fluorescence intensity to the reference value is less than 0.8 times.
[Table 1]

No.	Labeled antibody	Molar equivalent ratio of compound with respect to 1 equivalent of antibody	DOL	Fluorescence intensity (solution)
101	Compound (1) - IgG	10 equivalents	3.1	C
		15 equivalents	4.1	B
		20 equivalents	5.9	A
102	Compound (2) - IgG	10 equivalents	3.3	C
		15 equivalents	4.2	B
		20 equivalents	5.8	A
103	Compound (3) - IgG	10 equivalents	3.2	A
		15 equivalents	4.1	AA
		20 equivalents	6.0	AAA
104	Compound (6) - IgG	10 equivalents	3.1	AA
		30 equivalents	4.3	AAA
c11	Comparative compound (1) - IgG	10 equivalents	3.0	1.0 (reference value)
		15 equivalents	4.6	F
		20 equivalents	5.7	G
c12	Comparative compound (2) - IgG	10 equivalents	3.1	F
		15 equivalents	4.0	E
		20 equivalents	5.9	D

[2] Evaluation of dot blot fluorescence intensity
• Human-derived transferrin (20 mg/mL) was adjusted to 50 ng/mL with a TBS-T buffer solution, and 2 µL thereof was carefully spotted on a nitrocellulose membrane. The membrane was dried and then blocked in TBS-T with a Fish Gelatin blocking buffer solution. Subsequently, 6 µL of a polyclonal rabbit anti-human transferrin antibody was added to 30 mL of a PBS-T buffer solution, the membrane was immersed therein, and shaking was carried out for 1 hour. Then, the membrane was taken out and washed with a TBS-T buffer solution four times. Then, 15 µL of the labeled antibody (anti-rabbit IgG) was added to 30 mL of a TBS-T buffer solution, the membrane was immersed therein, and incubation was carried out at room temperature for 1 hour with stirring. The membrane was washed 3 times with a TBS-T buffer solution for 10 minutes and finally washed with a TBS buffer solution for 10 minutes. The obtained membrane was dried on a hot plate at 40°C for 1 hour and imaged using an Amersham Typhoon scanner (manufactured by Cytiva) with excitation light of 785 nm under the uniform exposure conditions, thereby calculating the fluorescence intensity in a fluorescence wavelength range of 810 to 840 nm. Using the integrated value of the fluorescence intensity of the comparative compound (1) - IgG having DOL of 3.0 (addition of 10 equivalents of dye) in a fluorescence wavelength range of 810 to 840 nm as the reference value, the ratio to this reference value (the integrated value of the fluorescence intensity of the labeled antibody in a fluorescence wavelength range of 810 to 840 nm/the reference value) was calculated, and evaluation was carried out based on the following evaluation standards. The results are summarized in Table 2.
- Evaluation standards for fluorescence intensity (integrated value) -
• AAA: The ratio of fluorescence intensity to the reference value is 2.4 times or more.
• AA: The ratio of fluorescence intensity to the reference value is 2.2 times or more and less than 2.4 times.
• A: The ratio of fluorescence intensity to the reference value is 2.0 times or more and less than 2.2 times.
• B: The ratio of fluorescence intensity to the reference value is 1.8 times or more and less than 2.0 times.
• C: The ratio of fluorescence intensity to the reference value is 1.5 times or more and less than 1.8 times.
• D: The ratio of fluorescence intensity to the reference value is 1.3 times or more and less than 1.5 times.
• E: The ratio of fluorescence intensity to the reference value is 1.1 times or more and less than 1.3 times.
• F: The ratio of fluorescence intensity to the reference value is 0.8 times or more and less than 1.1 times.
• G: The ratio of fluorescence intensity to the reference value is less than 0.8 times.
[Table 2]

No.	Labeled antibody	Molar equivalent ratio of compound with respect to 1 equivalent of antibody	DOL	Fluorescence intensity (dot blot)
201	Compound (1) - IgG	10 equivalents	3.1	C
		15 equivalents	4.1	B
		20 equivalents	5.9	A
202	Compound (2) - IgG	10 equivalents	3.3	C
		15 equivalents	4.2	B
		20 equivalents	5.8	A
203	Compound (3) - IgG	10 equivalents	3.2	A
		15 equivalents	4.1	AA
		20 equivalents	6.0	AAA
c21	Comparative compound (1) - IgG	10 equivalents	3.0	1.0 (reference value)
		15 equivalents	4.6	F
		20 equivalents	5.7	G
c22	Comparative compound (2) - IgG	10 equivalents	3.1	F
		15 equivalents	4.0	E
		20 equivalents	5.9	D

[3] Evaluation of fluorescence intensity in Western blotting
• Transferrin (manufactured by Merck KGaA) was diluted with a Fluorescent Compatible Sample Buffer (4X, non-reducing) (manufactured by Thermo Fisher Scientific, Inc.) to 1 ng/uL, 0.3 ng/uL, or 0.1 ng/µL, followed by heating treatment at 95°C for 5 minutes. The above-described transferrin sample and a PageRuler Prestained NIR Protein Ladder (manufactured by Thermo Fisher Scientific, Inc.) were loaded on Novex 4-20% Tris-Glycine Mini Gels (manufactured by Thermo Fisher Scientific, Inc.), and then electrophoresis was carried out at a constant voltage of 225 V for 45 minutes. The gel after electrophoresis and a nitrocellulose membrane (manufactured by Cytiva) were superimposed, protein transfer was carried out at a constant voltage of 12 V for 1 hour, and then the membrane was immersed in a Western Blot Blocking Buffer (Fish Gelatin) (manufactured by TAKARA Bio Inc.) and allowed to stand at 4°C for 12 hours. After washing with a TBS-T buffer, the membrane was immersed in a solution containing a primary antibody for transferrin (manufactured by Dako Corporation) (diluted 5,000 times), shaking was carried out for 1 hour, and the membrane was washed with the TBS-T buffer. A solution of the comparative compound (1) - IgG (diluted 25,000 times) was adjusted, and the membrane was immersed and shaken for 1 hour in a light-shielded state, followed by washing with TBS-T. The membrane was shielded from light for 1 hour in a constant-temperature tank at 40°C and then dried. Imaging was carried out using an Amersham Typhoon scanner (manufactured by Cytiva), and with excitation light of 785 nm under the uniform measurement conditions, the fluorescence intensity of a fraction of 3.24 mm² in a fluorescence wavelength range of 810 to 840 nm was measured and used as a signal fluorescence intensity. The fluorescence intensity of the antibodies labeled with other compounds was measured in the same manner as described above.
• Using the integrated value of the signal fluorescence intensity of the comparative compound (1) - IgG having DOL of 3.0 (addition of 10 equivalents of dye) in a fluorescence wavelength range of 810 to 840 nm as the reference value, the ratio to this reference value (the integrated value of the signal fluorescence intensity of the labeled antibody in a fluorescence wavelength range of 810 to 840 nm/the reference value) was calculated, and evaluation was carried out based on the following evaluation standards. The results are summarized in Table 3.
- Evaluation standards for fluorescence intensity (integrated value) -
1. A: The ratio of signal fluorescence intensity to the reference value is 2.0 times or more.
2. B: The ratio of signal fluorescence intensity to the reference value is 1.8 times or more and less than 2.0 times.
3. C: The ratio of signal fluorescence intensity to the reference value is 1.5 times or more and less than 1.8 times.
4. D: The ratio of signal fluorescence intensity to the reference value is 1.3 times or more and less than 1.5 times.
5. E: The ratio of signal fluorescence intensity to the reference value is 1.1 times or more and less than 1.3 times.
6. F: The ratio of signal fluorescence intensity to the reference value is 0.9 times or more and less than 1.1 times.
7. G: The ratio of signal fluorescence intensity to the reference value is less than 0.9 times.
[Table 3]

No.	Labeled antibody	Molar equivalent ratio of compound with respect to 1 equivalent of antibody	DOL	Fluorescence intensity in Western blotting
301	Compound (2) - IgG	10 equivalents	3.3	D
		15 equivalents	4.2	C
		20 equivalents	5.8	B
302	Compound (3) - IgG	10 equivalents	3.2	D
		15 equivalents	4.1	C
		20 equivalents	6.0	B
303	Compound (6) - IgG	10 equivalents	3.1	B
		30 equivalents	4.3	A
c31	Comparative compound (1) - IgG	10 equivalents	3.0	1.0 (reference value)
		15 equivalents	4.6	F
		20 equivalents	5.7	G
c32	Comparative compound (2) - IgG	10 equivalents	3.1	F
		15 equivalents	4.0	E
		20 equivalents	5.9	D

• From the results in Tables 1 to 3 above, the following facts can be seen.
• Although having two phosphor moieties, the comparative compound (1) does not include the nitrogen-containing saturated 5-membered ring structure represented by General Formula (i) and does not include, as a substituent, a polyalkyleneoxy structure represented by -(L-O)_gR^E, and thus it is not the compound defined in the present invention in that it does not have the structure represented by General Formula (I). In the labeled antibody obtained by using this comparative compound (1), all of the solution fluorescence intensity, the dot blot fluorescence intensity, and the Western blotting fluorescence intensity are low (Nos. c11, c21, and c31).
• Although having two phosphor moieties, the comparative compound (2) does not include the nitrogen-containing saturated 5-membered ring structure represented by General Formula (i), and thus it is not the compound defined in the present invention in that it does not have the structure represented by General Formula (I). Although the fluorescence intensity is slightly improved as compared with a case where the comparative compound (1) is used in that the labeled antibody obtained by using this comparative compound (2) includes, as a substituent, a polyalkyleneoxy structure represented by -(L-O)_gR^E, the fluorescence intensity is not sufficient. (Nos. c12, c22, and c32 with respect to Nos. c11, c21, and c31).
• On the other hand, in at least any form of the solution or the dot blot, all of the antibodies labeled with the compounds (1) to (3) and (6), which are the compounds according to the embodiment of the present invention, have a fluorescence intensity of 1.5 times or more with respect to the fluorescence intensity of the antibody labeled with the comparative compound (1) have a fluorescence intensity of 1.3 times or more even in the form of the Western blotting fluorescence intensity, and thus exhibit an excellent fluorescence intensity. Moreover, the decrease in the fluorescence intensity associated with the increase in DOL is also suppressed (Nos. 101 to 104 with respect to No. c11, Nos. 201 to 203 with respect to No. c21, and Nos. 301 to 303 with respect to No. c31). From the comparison between the compounds (1) and (2), it has been found that an excellent fluorescence intensity is exhibited even in a case where the group including -(L-O)_gR^E is present either on the ring of the nitrogen-containing saturated 5-membered ring represented by General Formula (i) or on the linking group moiety of this nitrogen-containing saturated 5-membered ring. In addition, from the comparison between the compounds (2) and (3), it has been found that even in a case where the number of phosphor moieties in the compound is increased, the same level of the excellent fluorescence intensity is exhibited in terms of the fluorescence intensity per one phosphor moiety.
• As described above, since the compound according to the embodiment of the present invention is a compound including at least two phosphor moieties and the specific structure represented by General Formula (I), it can impart an excellent fluorescence intensity to a labeled biological substance to be obtained, in at least any form of the solution, the dot blot, or the Western blotting.
• The present invention has been described together with the embodiments of the present invention. However, the inventors of the present invention do not intend to limit the present invention in any part of the details of the description unless otherwise specified, and it is conceived that the present invention should be broadly construed without departing from the spirit and scope of the invention shown in the attached "WHAT IS CLAIMED IS".
• This application claims priority based on JP2021-141999 filed in Japan on August 31, 2021 , and JP2022-100573 filed in Japan on June 22, 2022 , which are incorporated herein by reference as a part of the description regarding the present specification.

Claims (15)

1. A compound comprising:

   at least two phosphor moieties; and

   a structure represented by General Formula (I),

   

   in the formula, X¹ to X³ represent -O-, -S-, >NR¹, or >CR²R³,

   R¹ to R³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, -(L-O)_gR^E, an acyl group, -NR⁸R⁹, or -OR¹⁰,

   R⁸ to R¹⁰ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an aryl group, a heteroaryl group, or -(L-O)_gR^E, where L represents an alkylene group, R^E represents a hydrogen atom or an alkyl group, and g is 1 to 24,

   L^a and L^b represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B, where R^A and R^B represent a hydrogen atom or a substituent,

   n is an integer of 2 or more,

   provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and/or at least one of L^a or L^b is a group having, as a substituent, a group including -(L-O)_gR^E,

   the -(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance, and

   * represents a bonding site.
2. The compound according to claim 1,

   wherein the compound is represented by General Formula (II),

   

   in the formula, R⁴ and R⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group,

   R⁶ and R⁷ represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, an amino group, an acyl group, a heteroaryl group, an anionic group, a cationic group, or Q, where Q represents a carboxy group, a substituent capable of being bonded to a biological substance, or a substituent capable of being bonded to a solid support,

   L¹ and L⁶ represent an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, or >P(=O)OR^B,

   L² and L⁵ represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B,

   M represents the phosphor moiety, a physiologically active substance moiety, a prodrug moiety, or a radioactive isotope-containing moiety,

   provided that at least two of M's represent the phosphor moiety,

   m is an integer of 1 or more,

   X¹ to X³, R¹ to R³, L^a, L, R^A, R^B, R^E, g, and n respectively have the same meanings as X¹ to X³, R¹ to R³, L^a, L, R^A, R^B, R^E, g, and n described above,

   provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and/or at least one of L^a, L³, or, L⁴ is a group having, as a substituent, a group including -(L-O)_gR^E, and

   the-(L-O)_gR^E in R¹ to R³, L^a, L³, and L⁴, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
3. The compound according to claim 2,

   wherein the compound is represented by General Formula (III),

   

   in the formula, Y¹ to Y³, Z¹ to Z³, and W¹ to W³ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group,

   LL¹ and LL² represent a single bond or a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B,

   s, t, and u are an integer of 0 or more,

   R¹ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, L, R^A, R^B, R^E, g, n, and m respectively have the same meanings as R¹ to R⁷, L¹, L², L⁵, L⁶, X¹ to X³, M, L, R^A, R^B, R^E, g, n, and m described above,

   provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and/or at least one of Y¹, Y², Y³, Z¹, Z², Z³, W¹, W², or W³ is a group including -(L-O)_gR^E, and

   the -(L-O)_gR^E in R¹ to R³, Y¹ to Y³, Z¹ to Z³, and W¹ to W³, which include -(L-O)_gR^E, is not bonded to at least any one of a phosphor or a biological substance.
4. The compound according to claim 3,

   wherein the compound is represented by General Formula (IV),

   

   in the formula, R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q,

   provided that at least one of R^6A or R^7A represents Q,

   L⁷ and L⁸ represent a linking group obtained by combining one or two or more of an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -O-, -S-, >C=O, >NR^A, >S=O, >S(=O)₂, and >P(=O)OR^B,

   Y⁴ and Y⁵ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an acyl group, an amino group, a hydroxy group, an alkoxy group, a sulfanyl group, an aryl group, or a heteroaryl group, and

   R⁴, R⁵, L², L⁵, X¹ to X³, Y¹ to Y³, Z¹ to Z³, W¹ to W³, M, Q, R^A, R^B, n, m, s, t, and u respectively have the same meanings as R⁴, R⁵, L², L⁵, X¹ to X³, Y¹ to Y³, Z¹ to Z³, W¹ to W³, M, Q, R^A, R^B, n, m, s, t, and u described above.
5. The compound according to claim 3 or 4,

   wherein at least one of the following condition (Z1), (Z2), or (Z3) is satisfied,

   the condition (Z1): the s is an integer of 1 or more, and at least one of the Y¹, the Z¹, or the W¹ is a group including -(L-O)_gR^E,

   the condition (Z2): the t is an integer of 1 or more, and at least one of the Y², the Z², or the W² is a group including -(L-O)_gR^E,

   the condition (Z3): the u is an integer of 1 or more, and at least one of the Y³, the Z³, or the W³ is a group including -(L-O)_gR^E.
6. The compound according to any one of claims 1 to 5,
   wherein the structure represented by General Formula (I) includes a structure in which X¹ to X³ are >CR²R³.
7. The compound according to claim 6,
   wherein in the structure in which X¹ to X³ are >CR²R³, where the structure is included in the structure represented by General Formula (I), at least one R² is -NR⁸R⁹ or -OR¹⁰.
8. The compound according to claim 7,
   wherein in a structure in which X¹ to X³ are >CR²R³ and at least one R² is -NR⁸R⁹, or -OR¹⁰, where the structure is included in the structure represented by General Formula (I), at least one of R⁸, R⁹, or R¹⁰ is a group including -(L-O)_gR^E.
9. The compound according to claim 2,

   wherein the compound is represented by General Formula (V),

   

   in the formula, X⁴ to X⁹ represent -O-, -S-, >NR¹⁰¹, or >CR¹⁰²R¹⁰³,

   provided that one of X⁴, X⁵, or X⁶ is a carbon atom or a nitrogen atom, which has -L¹⁰-M as any one of R¹⁰¹, R¹⁰², or R¹⁰³, and one of X⁷, X⁸, or X⁹ is a carbon atom or a nitrogen atom, which has -L¹¹-M as any one of R¹⁰¹, R¹⁰², or R¹⁰³,

   R¹⁰¹ to R¹⁰³, which are neither -L¹⁰-M nor -L¹¹-M, represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an acyl group, -NR⁸R⁹, -OR¹⁰, or an anionic group,

   L¹⁰ and L¹¹ represent a single bond or a divalent linking group,

   R¹ to R³, R⁶ to R¹⁰, X¹ to X³, M, n, and m respectively have the same meanings as R¹ to R³, R⁶ to R¹⁰, X¹ to X³, M, n, and m described above,

   provided that a structure parenthesized in ( )_n has at least any one of >NR¹ or >CR²R³, and at least one of R¹, R², or R³ contained in the structure parenthesized in ( )_n is a group including -(L-O)_gR^E, and

   R¹ to R³ which include the -(L-O)_gR^E are not bonded to at least any one of a phosphor or a biological substance.
10. The compound according to claim 9,

    wherein the compound is represented by General Formula (VI),

    

    in the formula, R^6A and R^7A represent a hydrogen atom, a hydroxy group, a sulfanyl group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, a heteroaryl group, an amino group, an acyl group, an anionic group, a cationic group, or Q,

    provided that at least one of R^6A or R^7A represents Q,

    L¹² and L¹³ represent a linking group,

    na and nb are integers of 0 or more, and

    L¹⁰, L¹¹, X¹ to X⁹, M, Q, n, and m respectively have the same meanings as L¹⁰, L¹¹, X¹ to X⁹, M, Q, n, and m described above,

    provided that any structure parenthesized in ( )_n, ( )_na, or ( )_nb has at least any one of >NR¹ or >CR²R³, and each of the structures parenthesized in ( )_n, ( )_na, and ( )_nb has a group including -(L-O)_gR^E, as at least one of R¹, R², or R³, and

    R¹ to R³ which include the -(L-O)_gR^E are not bonded to at least any one of a phosphor or a biological substance.
11. The compound according to claim 10,

    wherein (A) the na is an integer of 1 or more, and the R^6A is the Q, and/or

    (B) the nb is an integer of 1 or more, and the R^7A is the Q,

    provided that the number of shortest linking atoms of the L¹³ is 7 or less in a case of the (A), and the number of shortest linking atoms of the L¹² is 7 or less in a case of the (B).
12. The compound according to any one of claims 9 to 11,
    wherein the structure represented by General Formula (I) includes a structure in which X¹ to X³ are >CR²R³.
13. The compound according to claim 12,
    wherein in the structure in which X¹ to X³ are >CR²R³, where the structure is included in the structure represented by General Formula (I), at least one R² is -NR⁸R⁹ or -OR¹⁰.
14. A labeled biological substance that is obtained by bonding the compound according to any one of claims 1 to 13 to a biological substance.
15. The labeled biological substance according to claim 14,
    wherein the biological substance is any one of a protein, an amino acid, a nucleic acid, a nucleotide, a sugar chain, or a phospholipid.